Standartize FOCIL metrics across CL clients

[KatyaRyazantseva]

This issue aims to open a discussion and identify the standardized list of metrics for CL clients to monitor and measure EIP-7805: FOCIL on the consensus layer side.

Processes that could me measured:

• inclusion list byte size
• inclusion list construction time
• inclusion list validation time
• execution payload validation time
• number of inclusion lists received from the network
• number of inclusion lists stored in the cache
• equivocation cases

Questions:

• Should we monitor the cache after the deadline for potential errors? (We might split metrics into before/after deadline.)
• Should we store the number of transactions at each step? For example, before and after validation on slot N+1.

Example metrics:

• beacon_inclusion_list_construction_{time} (histogram)
• beacon_inclusion_list_bytes_size (counter)
• beacon_inclusion_list_update_payload_{time} (histogram)
• beacon_inclusion_list_payload_validation_{time} (histogram)
• beacon_commitee_inclusion_list_received_total (counter)
• beacon_commitee_inclusion_list_stored_total (counter)

Any thoughts and suggestions on this are welcome.