state_history_plugin LIB notification lags LIB

[heifner]

The state_history_plugin get_blocks_result_v0 last_irreversible lags behind actual LIB by ~500ms as LIB is updated after the accepted_block signal which is used to send out the get_blocks_result_v0 message.

PR #8927 fixes a similar problem with get_blocks_result_v0 head lagging behind actual head by ~500ms by using the signaled head instead of reaching back into the controller and accessing the current head which has not been updated at the time of the signal.

To fix this problem, signal'ed methods should not reach back into the controller for information not contained in the signal as there is no current guarantee of the values during these signals.