[1.0-beta4 -> main] P2P: Fix fork check on connection

[heifner]

If running without a block log or with a truncated block log, it is possible that trying to retrieve a block by number will fail because the block is not available in the block log. Modify on-fork check on first handshake to allow for the block not to be found. Also allow for block not to be found on sync check in case LIB moves during sync check.

Merges release/1.0-beta4 into main including #466

Resolves #456

[ericpassmore]

Note:start
group: STABILITY
category: INTERNALS
summary: More robust syncing to handle unavailable blocks, when client does not have backing blocklog.
Note:end