It removes 2 unused flags:
 - BIP9CheckMasternodesUpgraded from CChainParams
 - check_mn_protocol from versionbitsinfo

These flags have no meaning since 17c792c (PR dashpay#2594)

The TODO in removed code is super-seeded by new way to validate MN version
in hard-fork (see dashpay#5469 and DIP0023 for more details)

## Issue being fixed or feature implemented
During implementation #5469 (master node hard-fork) I noticed that some
parts of `CChainParams` are deprecated and can be removed.

## What was done?
1. removed methods from `CChainParams` that have no implementation at
all:
 - UpdateSubsidyAndDiffParams
 - UpdateLLMQChainLocks
 - UpdateLLMQTestParams
 - UpdateLLMQDevnetParams
2. removed method `BIP9CheckMasternodesUpgraded` from `CChainParams` and
a flag `check_mn_protocol` from `versionbitsinfo`.
(to follow-up #2594)


## How Has This Been Tested?
Run functional/unit tests.

## Breaking Changes
N/A


## Checklist:
- [x] I have performed a self-review of my own code
- [ ] I have commented my code, particularly in hard-to-understand areas
- [ ] 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)_

## Issue being fixed or feature implemented
Current implementation of MnEhfTx is not matched with DIP-0023, this PR
fixes it. It is a prior work for
#5469

## What was done?
- requestID is fixed from `clsig{quorumHeight}` to `mnhf{versionBit}` +
fixes for signature validation properly
 - v20 is minimal height to accept MnEHF special transactions
- versionBit is not BLS version - removed unrelated wrong code and
validations
- TxMempool will accept MnEHF transaction even if inputs/outputs are
zeroes and no fee
- implemented python's serialization/deserialization of MnEHF
transactions for future using in functional tests
 

## How Has This Been Tested?
Run functional/unit tests. Beside that there's new functional test in
#5469 that actually test format of
transaction and signature validation - to be merged later.

## Breaking Changes
Payload of MnEhf tx is changed, related consensus rules are changed.


## 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
- [x] I have made corresponding changes to the documentation
- [x] I have assigned this pull request to a milestone

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)_

---------

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

## Issue being fixed or feature implemented
Addressed issues and comments from [PR
comment](#5469 (comment))
and [PR
comment](#5469 (comment))

`Params()` should be const; global variable `CMNHFManager` is a better
out-come.


## What was done?
The helpers and direct calls of `UpdateMNParams` for each block to
update non-constant member in `Params()` is not needed anymore. Instead
`CMNHFManager` takes cares about status of Signals for each block,
update them dynamically and save in evo db.


## How Has This Been Tested?
Run unit/functional tests.

## Breaking Changes
Changed rpc `getblockchaininfo`. 
the field `ehf` changed meaning: it's now only a flag -1/0; but it is
introduced a new field `ehf_height` now that a height.


## 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

---------

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

* docs: update mnhf with details of final implementation

Relates to dashpay/dash#5469 and dashpay/dash#5505

* doc: misc updates and corrections

* docs: typo fix

* docs: deprecate MSG_LEGACY_TXLOCK_REQUEST

Aligns with dashpay/dash#5483

* chore: update link to prev version of docs

* docs: update mnlistdiff nversion location

Relates to dashpay/dash#5450

* docs(p2p): update mnlistdiff

Relates to dashpay/dash#5377

* docs: update cbtx for v3

Relates to dashpay/dash#5262

* docs: update mnhf with details of final implementation

Relates to dashpay/dash#5469 and dashpay/dash#5505

* docs: note removal of NODE_GETUTXO

Relates to dashpay/dash#5500

* chore: revert "docs: update mnhf with details of final implementation"

This reverts commit 8e4bf6c since there
may still be additional changes to the implementation (it's not merged)

* docs: update mnhf with details of final implementation

Relates to dashpay/dash#5469 and dashpay/dash#5505

* doc: misc updates and corrections

* docs: typo fix