[1.0-beta4 -> main] P2P: Fix sync stopping making progress

[heifner]

When all blocks of a requested range were received before any of them had been applied, the sync_next_expected_num would not make progress. This caused the node to not ever request the next range of blocks.

• Sync timer was always being canceled in recv_block making it effectively useless if any block at all was received
• Existing p2p_sync_throttle_test.py is a good test for the sync timer as it does not sync fast enough and the timer fires.
  • Increased timeout in test because sync timer now works correctly and causes the test to close connection and reconnect.
• Fixes for reset on failure in request_next_chuck()
  • Was not clearing out all sync variables
  • This also fixes test failure: p2p_sync_throttle_test #462
• Fix for calling sync manager for block received before LIB
  • Allows sync manager to properly account for the received block
• Includes removal of unused last_req and simplification of sync timer.

Merges release/1.0-beta4 into main including #469

Resolves #459
Resolves #462

Still investigating, but may also resolve #436

[ericpassmore]

Note:start
group: STABILITY
category: INTERNALS
summary: Improve Syncing to handle condition where blocks were received before being applied. Previously this condition caused the node to not ever request the next range of blocks.
Note:end