go/consensus/tendermint: Sync state database before discarding versions

[kostko]

Otherwise a crash can cause the state database to be rolled back to a version
that has already been discarded from Tendermint's state stores which would
prevent replay on restart.

Discovered during long-term tests.

[codecov]

Codecov Report

Merging #3173 into master will increase coverage by 0.10%.
The diff coverage is 33.33%.

@@            Coverage Diff             @@
##           master    #3173      +/-   ##
==========================================
+ Coverage   68.70%   68.81%   +0.10%     
==========================================
  Files         385      385              
  Lines       37945    37951       +6     
==========================================
+ Hits        26072    26115      +43     
+ Misses       8575     8536      -39     
- Partials     3298     3300       +2     

Impacted Files	Coverage Δ
go/consensus/tendermint/abci/prune.go	78.57% <0.00%> (-1.64%)	⬇️
go/storage/mkvs/db/api/api.go	57.77% <0.00%> (-2.69%)	⬇️
go/storage/mkvs/db/badger/badger.go	70.43% <100.00%> (+0.12%)	⬆️
go/worker/common/p2p/error/error.go	71.42% <0.00%> (-28.58%)	⬇️
go/consensus/tendermint/api/errors.go	86.66% <0.00%> (-13.34%)	⬇️
go/consensus/tendermint/full/services.go	78.90% <0.00%> (-9.38%)	⬇️
go/consensus/tendermint/abci/state/state.go	61.53% <0.00%> (-7.70%)	⬇️
go/consensus/tendermint/epochtime/epochtime.go	78.78% <0.00%> (-7.58%)	⬇️
.../consensus/tendermint/apps/epochtime_mock/state.go	74.46% <0.00%> (-4.26%)	⬇️
go/keymanager/client/client.go	82.64% <0.00%> (-4.14%)	⬇️
... and 42 more

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