Open more dbs if necessary

[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)

• In order to have the complete state, we need 2 trie dbs marked as active. When restarting the node, we have to be sure that a minimum of 2 trie dbs marked as active are also opened, else the node will not have access to the entire state.

Proposed Changes

• When a node is restarting, opend trie dbs until there are a minimum of 2 that are marked as active (if the trie was synced, only one db marked as active is needed)

Testing procedure

• Restart a node after there is a snapshot that takes more than one epoch, and check that the dbs are opened and closed correctly (this will be tested on a different branch, in which a time.Sleep() is added in order to force the snapshot process to take more than an epoch)

[codecov-commenter]

Codecov Report

Merging #4366 (675c3e3) into rc/v1.4.0 (c6101b4) will increase coverage by 0.00%. The diff coverage is 77.68%.

@@            Coverage Diff             @@
##           rc/v1.4.0    #4366   +/-   ##
==========================================
  Coverage      73.84%   73.84%           
==========================================
  Files            686      688    +2     
  Lines          88038    88087   +49     
==========================================
+ Hits           65011    65049   +38     
- Misses         18118    18130   +12     
+ Partials        4909     4908    -1     

Impacted Files	Coverage Δ
factory/processComponents.go	53.18% <0.00%> (-0.06%)	:arrow_down:
storage/factory/pruningStorerFactory.go	0.00% <0.00%> (ø)
storage/pruning/pruningStorer.go	73.58% <86.11%> (+0.17%)	:arrow_up:
epochStart/bootstrap/metaStorageHandler.go	72.85% <100.00%> (+0.19%)	:arrow_up:
epochStart/bootstrap/process.go	85.34% <100.00%> (+0.01%)	:arrow_up:
epochStart/bootstrap/shardStorageHandler.go	87.80% <100.00%> (+0.02%)	:arrow_up:
factory/dataComponents.go	53.53% <100.00%> (+0.47%)	:arrow_up:
storage/pruning/fullHistoryTriePruningStorer.go	91.66% <100.00%> (+0.36%)	:arrow_up:
storage/pruning/persistersTracker.go	100.00% <100.00%> (ø)
storage/pruning/triePersistersTracker.go	100.00% <100.00%> (ø)
... and 2 more

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