blockchain/v0: relax termination conditions and increase sync timeout

[melekes]

Closes: #5718

[codecov]

Codecov Report

Merging #5741 (c15b89c) into master (0d108ad) will decrease coverage by 0.16%.
The diff coverage is 63.36%.

@@            Coverage Diff             @@
##           master    #5741      +/-   ##
==========================================
- Coverage   60.48%   60.32%   -0.17%     
==========================================
  Files         259      259              
  Lines       23334    23345      +11     
==========================================
- Hits        14114    14083      -31     
- Misses       7754     7783      +29     
- Partials     1466     1479      +13     

Impacted Files	Coverage Δ
blockchain/v2/io.go	0.00% <0.00%> (ø)
blockchain/v2/reactor.go	35.31% <33.33%> (+1.85%)	⬆️
blockchain/v0/reactor.go	63.96% <72.30%> (-0.57%)	⬇️
blockchain/v0/pool.go	77.18% <73.68%> (-1.79%)	⬇️
privval/signer_listener_endpoint.go	80.00% <0.00%> (-9.42%)	⬇️
privval/socket_listeners.go	78.72% <0.00%> (-4.26%)	⬇️
privval/secret_connection.go	72.68% <0.00%> (-3.61%)	⬇️
privval/signer_endpoint.go	75.75% <0.00%> (-3.04%)	⬇️
consensus/reactor.go	74.08% <0.00%> (-2.52%)	⬇️
... and 8 more