test(contracts): Add a test for block hash in logs

The cost of running benchmarks was determined by running them on the contracts at regenesis/0.4.0 (98e02cfa/ PR #1148), then applied to the benchmarks here to calculate both absolute and relative amounts saed

I observed a very small savings from increasing the optimizer runs,
and no noticable impact on compile time

Although we're quite happy when the CTC gets cheaper, we want to know about it
and lock-in the savings.

Previously our gas specs have only printed the values they record,
without ensuring that the cost doesn't drift up over time. Adding expectApprox will allow these costs to decrease, but not increase.

Previously the sequencer would call the `syncBatchesToTip` method
as part of its `sequence()` loop. This commit removes that as the
call to `syncBatchesToTip` does nothing for the sequencer currently.
Syncing the batches would be useful for triggering reorgs, but
that functionality does not currently exist. It would be better to
remove this functionality for now as it could potentially interfere
with the locking mechanism introduced in
dfaa8fc20f586265f0a5c07ca76c6c793ba49157.

This will also reduce the amount of time the `txLock` is held, meaning
that less transactions sent via RPC will be blocked and held in memory
while waiting to execute.

to message-relayer and integration-tests

and remove SafeMath from 0.8 GasPriceOracle contract

as these serve as integration points for projects

as activated by default in 0.8

https://docs.soliditylang.org/en/v0.8.0/control-structures.html#checked-or-unchecked-arithmetic

Breaking change in v0.8.0