Implementation EHF mechanism, part 4. Previous changes are: 
 - #4577
 - #5505
 - #5469

## Issue being fixed or feature implemented
Currently MN_RR is activated automatically by soft-fork activation after
v20 is activated.
It is not flexible enough, because platform may not be released by that
time yet or in opposite it can be too long to wait.
Also, any signal of EHF requires manual actions from MN owners to sign
EHF signal - it is automated here.

## What was done?
New spork `SPORK_24_MN_RR_READY`; new EHF manager that sign EHF signals
semi-automatically without manual actions; and send transaction with EHF
signal when signal is signed to network.
Updated rpc `getblockchaininfo` to return information about of EHF
activated forks.
Fixed function `IsTxSafeForMining` in chainlock's handler to skip
transactions without inputs (empty `vin`).

## How Has This Been Tested?
Run unit/functional tests. Some tests have been updated due to new way
of MN_RR activation: `feature_asset_locks.py`, `feature_mnehf.py`,
`feature_llmq_evo.py` and unit test `block_reward_reallocation_tests`.


## Breaking Changes
New way of MN_RR activation.

## Checklist:
- [x] I have performed a self-review of my own code
- [x] I have commented my code, particularly in hard-to-understand areas
- [x] I have added or updated relevant unit/integration/functional/e2e
tests
- [ ] I have made corresponding changes to the documentation
- [x] I have assigned this pull request to a milestone _(for repository
code-owners and collaborators only)_

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Co-authored-by: UdjinM6 <[email protected]>
Co-authored-by: PastaPastaPasta <[email protected]>