fix: save last finalized block

[fgimenez]

Closes #1712

Prevents potential issues with fixed finality depth on adverse conditions, there are no fixed bounds to finality depth and the actual finalized block can be earlier than a last_finalized_block_number initialized to a fixed value.

[mattsse]

lgtm, storing finalized is sound imo because finalized, hehe

pending @rkrasiuk

[joshieDo]

unwinds should probably clear this one out if it goes beyond this block. this can happen when manually calling unwind

[onbjerg]

makes sense to me

[mattsse]

unwinds should probably clear this one out if it goes beyond this block. this can happen when manually calling unwind

what are you suggesting? what needs to be done?

[joshieDo]

if there's a pipeline unwind that goes beyond that block, replace it with a lower one on Finish stage unwind fn

[fgimenez]

if there's a pipeline unwind that goes beyond that block, replace it with a lower one on Finish stage unwind fn

@joshieDo cool thx! we should save the lowest one that results from the unwind operation, right? either to-block or the lowest end resulting from num-blocks?

[fgimenez]

if there's a pipeline unwind that goes beyond that block, replace it with a lower one on Finish stage unwind fn

@joshieDo ok done here eaec49d by introducing a FinalizedBlockProvider trait with default methods, ptal