bug(dot/state): delete previous previous finalised trie from BlockState.tries

[timwu20]

Changes

• Deletes the previous trie after a block is finalised from BlockState.tries.
• Significantly reduces memory usage over time
• Added a tries set/delete gauge
• Removed gauge mocks from dot/state tests.

Tests

go test ./dot/state

Issues

• closes Delete previously finalised trie from BlockState.tries #2340

Primary Reviewer

• @noot

[codecov]

Codecov Report

Merging #2341 (cca78fd) into development (625cbcf) will increase coverage by 0.47%.
The diff coverage is 86.95%.

@@               Coverage Diff               @@
##           development    #2341      +/-   ##
===============================================
+ Coverage        57.55%   58.03%   +0.47%     
===============================================
  Files              212      213       +1     
  Lines            27952    28018      +66     
===============================================
+ Hits             16089    16259     +170     
+ Misses           10228    10118     -110     
- Partials          1635     1641       +6     

Flag	Coverage Δ
unit-tests	58.03% <86.95%> (+0.47%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
dot/state/test_helpers.go	49.76% <ø> (-0.24%)	⬇️
dot/state/block_finalisation.go	47.25% <83.33%> (+2.60%)	⬆️
dot/state/tries.go	100.00% <100.00%> (+7.31%)	⬆️
lib/babe/crypto.go	59.43% <0.00%> (-24.57%)	⬇️
dot/network/message.go	66.52% <0.00%> (-2.61%)	⬇️
dot/state/block.go	42.45% <0.00%> (-2.48%)	⬇️
dot/sync/chain_processor.go	48.04% <0.00%> (-1.67%)	⬇️
dot/network/light.go	85.25% <0.00%> (-0.80%)	⬇️
lib/babe/babe.go	3.58% <0.00%> (-0.02%)	⬇️
... and 12 more

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[qdm12]

Nice, although all the metrics testing removal hurts my soul, can you please adapt the test code to take care of the new metrics added?

Also please remove the tries gauge in favor of the new set and delete counter metrics

[noot]

nice!

[qdm12]

@noot can you merge this please? Thanks!