fa7e6c5 Add LIFETIMEBOUND to InitializeChainstate (MarcoFalke)
fa5c896 Add LIFETIMEBOUND to CScript where needed (MarcoFalke)

Pull request description:

  Without this, stack-use-after-scope can only be detected at runtime with ASan or code review, both of which are expensive.

  Use `LIFETIMEBOUND` to turn this error into a compile warning.

  See https://releases.llvm.org/12.0.0/tools/clang/docs/AttributeReference.html#lifetimebound

  Example:

  ```cpp
  const CScript a{WITH_LOCK(::cs_main, return CScript{} << OP_0 << OP_1)};
  ```

  Before: (no warning)
  After:

  ```
  warning: returning reference to local temporary object [-Wreturn-stack-address]
      const CScript a{WITH_LOCK(::cs_main, return CScript{} << OP_0 << OP_1)};
                                                  ^~~~~~~~~
  ./sync.h:276:65: note: expanded from macro 'WITH_LOCK'
  #define WITH_LOCK(cs, code) [&]() -> decltype(auto) { LOCK(cs); code; }()
                                                                  ^~~~

ACKs for top commit:
  theuni:
    utACK fa7e6c5.
  jonatack:
    Light ACK fa7e6c5 debug build with clang 13, reproduced the example compiler warning in the pull description, and briefly looked at `clang::lifetimebound` support in earlier versions of clang; it is in clang 7 (https://releases.llvm.org/7.0.0/tools/clang/docs/AttributeReference.html#lifetimebound-clang-lifetimebound), did not see references to it in earlier docs

Tree-SHA512: e915acdc4532445205b7703fab61a5d682231ace78ecfb274cb8523ca2bddefd85828f50ac047cfb1afaff92a331f5f7b5a1472539f999e30f7cf8ac8c3222f3

…)::start_time

4cb9d21 blockstorage: add LIFETIMEBOUND to GetFirstStoredBlock()::start_time (Jon Atack)

Pull request description:

  Suggested in #25016 (comment), the lifetimebound attribute here indicates that a resource owned by the `start_block` param of `CBlockIndex* BlockManager::GetFirstStoredBlock()` can be retained by the method's return value, which enables detecting the use of out-of-scope stack memory (ASan `stack-use-after-scope`) at compile time.

  See https://releases.llvm.org/12.0.0/tools/clang/docs/AttributeReference.html#lifetimebound and #22278 for related discussion, and #25040 for a similar example.

ACKs for top commit:
  MarcoFalke:
    review ACK 4cb9d21

Tree-SHA512: a3f5ef83ebb6f08555d7c89f2437a682071b4ad77a7aa3326b6d2282c909bf9fcf4dac6bf05ee1d9931f2102cad4a02df5468bde1cf377d7126e84e8541604dc

…dBlock()::start_time

4cb9d21 blockstorage: add LIFETIMEBOUND to GetFirstStoredBlock()::start_time (Jon Atack)

Pull request description:

  Suggested in bitcoin#25016 (comment), the lifetimebound attribute here indicates that a resource owned by the `start_block` param of `CBlockIndex* BlockManager::GetFirstStoredBlock()` can be retained by the method's return value, which enables detecting the use of out-of-scope stack memory (ASan `stack-use-after-scope`) at compile time.

  See https://releases.llvm.org/12.0.0/tools/clang/docs/AttributeReference.html#lifetimebound and bitcoin#22278 for related discussion, and bitcoin#25040 for a similar example.

ACKs for top commit:
  MarcoFalke:
    review ACK 4cb9d21

Tree-SHA512: a3f5ef83ebb6f08555d7c89f2437a682071b4ad77a7aa3326b6d2282c909bf9fcf4dac6bf05ee1d9931f2102cad4a02df5468bde1cf377d7126e84e8541604dc