Rough prototype sending fcU earlier

[michaelsproul]

Issue Addressed

This is option 2 from:

• Send fcU before fully importing block #7745

Proposed Changes

• Call the full recompute_head* routine in import_block so that fcU gets sent to the EL prior to the block being fully imported.
• To work around the assumptions of recompute_head (head block and state exist in store): pass the beacon block and state to the function.

Additional Info

There are multiple problems with the current implementation but I'm curious to see how much this basic approach nets us before going further trying to fix the issues. Incomplete list of current flaws:

• I broke the attester cache's handling of blobs and columns (easy to fix)
• TODO