Add block head cache

[tudor-malene]

Why this change is needed

there is a slight performance degradation on testnet.
The query for the block head is one potential cause

What changes were made as part of this PR

• cache the l1 head

[StefanIliev545]

LGTM, provided that the assumption here is that we cache the hash instead of the block, because its the responsibility of the storage interface to be doing this, correct?

[tudor-malene]

LGTM, provided that the assumption here is that we cache the hash instead of the block, because its the responsibility of the storage interface to be doing this, correct?

yeah. the storage caches stuff