Gossip decoupling

[realbigsean]

• PR: Decouple gossip #3950
• creating a new "observed cache" to filter duplicates
  • from Pawan:

  • The observed cache has a few more duties than the attestation and sync committee ones the cache contains incomplete components of a fully available block (i.e AvailabilityPendingBlock + 4 blobs). Once we get all the components, we essentially go from the AvailabilityPendingBlock to an AvailableBlock which we can process in fork choice

• create a blob reprocessing flow
• make the block reprocessing flow dependent on blobs
• new gossip validation conditions for singular blobs

[realbigsean]

resolved in #4092