Sync missing snapshot nodes

[BeniaminDrasovean]

Description of the reasoning behind the pull request (what feature was missing / how the problem was manifesting itself / what was the motive behind the refactoring)

• If a trie node is missing, the node will not be able to progress. In order to fix this, when the state snapshot process is triggered, also start a sync process that will sync missing trie nodes from the network.

Proposed Changes

• Add a trie syncer to accountsDB. The syncer will be triggered if there are any missing nodes during the snapshot process.

Testing procedure

• Check that everything works as before
• Do not save some trie nodes to storage, and check that they will be synced during snapshot

[codecov-commenter]

Codecov Report

Base: 73.41% // Head: 73.30% // Decreases project coverage by -0.11% :warning:

Coverage data is based on head (3796daf) compared to base (57fe4d9). Patch coverage: 50.00% of modified lines in pull request are covered.

Additional details and impacted files

@@              Coverage Diff              @@
##           rc/v1.4.0    #4367      +/-   ##
=============================================
- Coverage      73.41%   73.30%   -0.12%     
=============================================
  Files            655      659       +4     
  Lines          85340    85518     +178     
=============================================
+ Hits           62655    62686      +31     
- Misses         17841    17979     +138     
- Partials        4844     4853       +9     

Impacted Files	Coverage Δ
factory/consensusComponents.go	0.00% <0.00%> (ø)
node/nodeRunner.go	0.00% <0.00%> (ø)
process/txsimulator/wrappedAccountsDB.go	65.38% <0.00%> (-5.45%)	:arrow_down:
state/accountsDBApi.go	91.45% <0.00%> (-3.24%)	:arrow_down:
state/accountsDBApiWithHistory.go	89.21% <0.00%> (-3.65%)	:arrow_down:
state/errors.go	50.00% <ø> (ø)
trie/keyBuilder/disabledKeyBuilder.go	0.00% <0.00%> (ø)
trie/trieStorageManagerWithoutCheckpoints.go	83.33% <ø> (ø)
trie/extensionNode.go	70.46% <30.76%> (-0.93%)	:arrow_down:
trie/branchNode.go	78.26% <50.00%> (-0.55%)	:arrow_down:
... and 23 more

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

:umbrella: View full report at Codecov.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.