unrevert more of https://github.com/status-im/nimbus-eth2/pull/5765

[tersec]

Followup to #5833, which reverted more than strictly required. This keeps at module boundaries for simplicity, and restores:

• beacon_chain/gossip_processing/block_processor.nim
• beacon_chain/networking/peer_pool.nim

While keeping reverted from #5765

• beacon_chain/nimbus_beacon_node.nim
• beacon_chain/sync/request_manager.nim
• beacon_chain/sync/sync_manager.nim
• beacon_chain/sync/sync_queue.nim
• tests/test_sync_manager.nim

$ grep "Slot start" ~/nimbus_working.log | jq -r '[.slot, .head]|@tsv' | tail -n50
7499650	47d6925b:7499649
7499651	0910a130:7499650
7499652	59477fc5:7499651
7499653	74eb41b5:7499652
7499654	642b44a1:7499653
7499655	cb9c7df4:7499654
7499656	6fb4cfe6:7499655
7499657	4104e7fa:7499656
7499658	3a62101f:7499657
7499659	1fefec4b:7499658
7499660	1fefec4b:7499658
7499661	1fefec4b:7499658
7499662	1fefec4b:7499658
7499663	59be4b3f:7499662
7499664	59be4b3f:7499662
7499665	fcd4fc4b:7499664
7499666	fcd4fc4b:7499664
7499667	fcd4fc4b:7499664
7499668	10cecda5:7499667
7499669	63af8e2b:7499668
7499670	c06bd6ac:7499669
7499671	c06bd6ac:7499669
7499672	898cca36:7499671
7499673	0720e898:7499672
7499674	c2c5c2b4:7499673
7499675	9c6692ac:7499674
7499676	9c2134d2:7499675
7499677	0681ca19:7499676
7499678	9cae3fa3:7499677
7499679	9cae3fa3:7499677
7499680	41623e50:7499679
7499681	298942d7:7499680
7499682	298942d7:7499680
7499683	c760ba62:7499682
7499684	c760ba62:7499682
7499685	b9fcea8c:7499684
7499686	b9fcea8c:7499684
7499687	296dc050:7499686
7499688	296dc050:7499686
7499689	93ef15cf:7499688
7499690	ab4a66c5:7499689
7499691	137767f7:7499690
7499692	cbc64915:7499691
7499693	cbc64915:7499691
7499694	e1cf9859:7499693
7499695	a4e6c38d:7499694
7499696	ff798196:7499695
7499697	ff798196:7499695
7499698	c6ac2200:7499697
7499699	73dd625b:7499698

where repeated heads match https://goerli.beaconcha.in/epoch/234364 and https://goerli.beaconcha.in/epoch/234365 missing blocks exactly.

[github-actions]

Unit Test Results

         9 files  ±0    1 101 suites  ±0   27m 51s ⏱️ ±0s
  4 226 tests ±0    3 879 ✔️ ±0  347 💤 ±0  0 ❌ ±0 
16 873 runs  ±0  16 475 ✔️ ±0  398 💤 ±0  0 ❌ ±0 

Results for commit 6366112. ± Comparison against base commit 225ef5e.