Reject transactions that won't work on the fork by height
Reject transactions that won't work on the fork by height

Starting 2 hours (~12 blocks) before the fork based on op_return
(i.e. voluntary reply protection) we are going to reject access
to mempool.

Before the check was made based `miningForkTime.value` now we are
going to use uahfHeight.

Since the HF already happened this check is not so valuable IMHO
cause a this code will be exercised only during the sync up of new
node so we should just reject anything that is not signing using
SIGHASH_FORKID. The code has been just translated as is to ease
the review process and could be revised further in a future PR.

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