Stop the block synchronization after the first finalized block

[fab-10]

Description

The Merge spec says that an execution should behave like this after the switch to PoS:

Beginning with receiving the finalized block next to the FIRST_FINALIZED_BLOCK, the networking stack MUST remove the handlers corresponding to the following messages:

NewBlockHashes (0x01)
NewBlock (0x07)
Peers that keep sending these messages after the handlers have been removed SHOULD be disconnected.

currently Besu stop any block synchronization task when the TTD is reached, so it is not following the spec, and doing so is not able to easily recognize if a peer is still on PoW after TTD has been reached, and disconnect those peers.

Acceptance Criteria

Keep processing and sending

• NewBlockHashes (0x01)
• NewBlock (0x07)
  messages until the first finalized block is received from the CL

Versions (Add all that apply)

• Software version: besu-22.4.3-SNAPSHOT

[jflo]

PR 3944 has been reverted, re-opening issue.