Summary:
Fixes the following RPCExamples:
-> ExampleCli waitforblock (removed comma between arguments)
-> ExampleCli waitforblockheight (removed comma between arguments)
-> ExampleRpc waitforblockheight (removed quotation marks around integer argument)

This is a backport of Core [[bitcoin/bitcoin#18398 | PR18398]]

Test Plan:
```
ninja && src/bitcoind &
sleep 5
src/bitcoin-cli waitforblockheight 100 1000
src/bitcoin-cli waitforblock  "0000000000079f8ef3d2c688c244eb7a4570b24c9ed7b4a8c619eb02596f8862" 1000
```

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Differential Revision: https://reviews.bitcoinabc.org/D8884

…il" RPCs

ea98d9c rpc: fix/add missing RPCExamples for "Util" RPCs (Sebastian Falbesoner)

Pull request description:

  Similar to bitcoin/bitcoin#18398, this PR gives the RPCExamples in the RPC category "Util" (that currently contains `createmultisig`, `deriveaddresses`, `estimatesmartfee`, `getdescriptorinfo`, `signmessagewithprivkey`, `validateaddress`, `verifymessage`) some love by fixing one broken and adding three missing examples:
  - fixed `HelpExampleRpc` for `createmultisig` (disturbing escape characters and quotation marks)
  - added missing `HelpExampleRpc` for
      -  `deriveaddresses` (also put descriptor in a new string constant)
      - `estimatesmartfee`
      - `getdescriptorinfo` (also put descriptor in a new string constant)

  Output for `createmultisig` example on the master branch:
  ```
  $ curl --user __cookie__ --data-binary '{"jsonrpc": "1.0", "id": "curltest", "method": "createmultisig", "params": [2, "[\"03789ed0bb717d88f7d321a368d905e7430207ebbd82bd342cf11ae157a7ace5fd\",\"03dbc6764b8884a92e871274b87583e6d5c2a58819473e17e107ef3f6aa5a61626\"]"]}' -H 'content-type: text/plain;' http://127.0.0.1:8332/
  Enter host password for user '__cookie__':
  {"result":null,"error":{"code":-1,"message":"JSON value is not an array as expected"},"id":"curltest"}
  ```

  Output for `createmultisig` example on the PR branch:
  ```
  $ curl --user __cookie__ --data-binary '{"jsonrpc": "1.0", "id": "curltest", "method": "createmultisig", "params": [2, ["03789ed0bb717d88f7d321a368d905e7430207ebbd82bd342cf11ae157a7ace5fd","03dbc6764b8884a92e871274b87583e6d5c2a58819473e17e107ef3f6aa5a61626"]]}' -H 'content-type: text/plain;' http://127.0.0.1:8332/
  Enter host password for user '__cookie__':
  {"result":{"address":"3QsFXpFJf2ZY6GLWVoNFFd2xSDwdS713qX","redeemScript":"522103789ed0bb717d88f7d321a368d905e7430207ebbd82bd342cf11ae157a7ace5fd2103dbc6764b8884a92e871274b87583e6d5c2a58819473e17e107ef3f6aa5a6162652ae","descriptor":"sh(multi(2,03789ed0bb717d88f7d321a368d905e7430207ebbd82bd342cf11ae157a7ace5fd,03dbc6764b8884a92e871274b87583e6d5c2a58819473e17e107ef3f6aa5a61626))#4djp057k"},"error":null,"id":"curltest"}
  ```

ACKs for top commit:
  jonatack:
    ACK ea98d9c looked at the code, rebased to master, ran the helps, did not try running the added json-rpc examples

Tree-SHA512: d6ecb6da66f19517065453357d210102e2cc9f1f8037aeb6a9177ff036d0c21773dddf5e0acdbc71edbbde3026e4d1e7ce7c0935cd3e023c60f34e1b173b3299

ea98d9c rpc: fix/add missing RPCExamples for "Util" RPCs (Sebastian Falbesoner)

Pull request description:

  Similar to bitcoin#18398, this PR gives the RPCExamples in the RPC category "Util" (that currently contains `createmultisig`, `deriveaddresses`, `estimatesmartfee`, `getdescriptorinfo`, `signmessagewithprivkey`, `validateaddress`, `verifymessage`) some love by fixing one broken and adding three missing examples:
  - fixed `HelpExampleRpc` for `createmultisig` (disturbing escape characters and quotation marks)
  - added missing `HelpExampleRpc` for
      -  `deriveaddresses` (also put descriptor in a new string constant)
      - `estimatesmartfee`
      - `getdescriptorinfo` (also put descriptor in a new string constant)

  Output for `createmultisig` example on the master branch:
  ```
  $ curl --user __cookie__ --data-binary '{"jsonrpc": "1.0", "id": "curltest", "method": "createmultisig", "params": [2, "[\"03789ed0bb717d88f7d321a368d905e7430207ebbd82bd342cf11ae157a7ace5fd\",\"03dbc6764b8884a92e871274b87583e6d5c2a58819473e17e107ef3f6aa5a61626\"]"]}' -H 'content-type: text/plain;' http://127.0.0.1:8332/
  Enter host password for user '__cookie__':
  {"result":null,"error":{"code":-1,"message":"JSON value is not an array as expected"},"id":"curltest"}
  ```

  Output for `createmultisig` example on the PR branch:
  ```
  $ curl --user __cookie__ --data-binary '{"jsonrpc": "1.0", "id": "curltest", "method": "createmultisig", "params": [2, ["03789ed0bb717d88f7d321a368d905e7430207ebbd82bd342cf11ae157a7ace5fd","03dbc6764b8884a92e871274b87583e6d5c2a58819473e17e107ef3f6aa5a61626"]]}' -H 'content-type: text/plain;' http://127.0.0.1:8332/
  Enter host password for user '__cookie__':
  {"result":{"address":"3QsFXpFJf2ZY6GLWVoNFFd2xSDwdS713qX","redeemScript":"522103789ed0bb717d88f7d321a368d905e7430207ebbd82bd342cf11ae157a7ace5fd2103dbc6764b8884a92e871274b87583e6d5c2a58819473e17e107ef3f6aa5a6162652ae","descriptor":"sh(multi(2,03789ed0bb717d88f7d321a368d905e7430207ebbd82bd342cf11ae157a7ace5fd,03dbc6764b8884a92e871274b87583e6d5c2a58819473e17e107ef3f6aa5a61626))#4djp057k"},"error":null,"id":"curltest"}
  ```

ACKs for top commit:
  jonatack:
    ACK ea98d9c looked at the code, rebased to master, ran the helps, did not try running the added json-rpc examples

Tree-SHA512: d6ecb6da66f19517065453357d210102e2cc9f1f8037aeb6a9177ff036d0c21773dddf5e0acdbc71edbbde3026e4d1e7ce7c0935cd3e023c60f34e1b173b3299

…ght)

ef35604 rpc: fix broken RPCExamples for waitforblock(height) (Sebastian Falbesoner)

Pull request description:

  This PR fixes several broken RPCExamples from the "blockchain" category:
  - `HelpExampleCli` for `waitforblock` (disturbing comma between arguments)
  - `HelpExampleCli` for `waitforblockheight` (disturbing comma between arguments)
  - `HelpExampleRpc` for `waitforblockheight` (disturbing quotation marks around integer argument)

  Note that the CLI example for `waitforblockheight` would also work with the first argument in quotation marks (in contrast to the RPC example), but I removed them as well as they are not needed.

  Outputs for the non-working examples in the master branch:
  ```
  $ ./bitcoin-cli waitforblock "0000000000079f8ef3d2c688c244eb7a4570b24c9ed7b4a8c619eb02596f8862", 1000
  error code: -8
  error message:
  blockhash must be of length 64 (not 65, for '0000000000079f8ef3d2c688c244eb7a4570b24c9ed7b4a8c619eb02596f8862,')
  ```

  ```
  $ ./bitcoin-cli waitforblockheight "100", 1000
  error: Error parsing JSON:100,
  ```

  ```
  $ curl --user __cookie__ --data-binary '{"jsonrpc": "1.0", "id": "curltest", "method": "waitforblockheight", "params": ["100", 1000]}' -H 'content-type: text/plain;' http://127.0.0.1:8332/
  Enter host password for user '__cookie__':
  {"result":null,"error":{"code":-1,"message":"JSON value is not an integer as expected"},"id":"curltest"}
  ```

  Outputs for the fixed examples in the PR branch:
  ```
  $ ./bitcoin-cli waitforblock "0000000000079f8ef3d2c688c244eb7a4570b24c9ed7b4a8c619eb02596f8862" 1000
  {
    "hash": "0000000000000000000910ae4d56120e0ddd55c0552e80ed12dba147abc68080",
    "height": 622416
  }
  ```

  ```
  $ ./bitcoin-cli waitforblockheight 100 1000
  {
    "hash": "0000000000000000000910ae4d56120e0ddd55c0552e80ed12dba147abc68080",
    "height": 622416
  }
  ```

  ```
  $ curl --user __cookie__ --data-binary '{"jsonrpc": "1.0", "id": "curltest", "method": "waitforblockheight", "params": [100, 1000]}' -H 'content-type: text/plain;' http://127.0.0.1:8332/
  Enter host password for user '__cookie__':
  {"result":{"hash":"0000000000000000000910ae4d56120e0ddd55c0552e80ed12dba147abc68080","height":622416},"error":null,"id":"curltest"}
  ```

ACKs for top commit:
  fanquake:
    ACK ef35604

Tree-SHA512: b98c6681d1aa24b3ee3ef4ef450cb630082a9f8695af18f3b6d418e5b0b1e472b787ccf6397cd719b4d5fe0082ea5f1d0ca553c1cc56066ee2d288be34c601e3