fix(tests): remove sync_empty_state

[marcelo-gonzalez]

This test can fail with nightly features and block PR merges: https://nayduck.nearone.org/#/test/231517. The reason it fails is that it sets up a node with a real rocksdb database in a temp dir, and creating snapshots actually takes several seconds even with small state because this loop takes a while. So the node trying to state sync can't request parts from the other node because it doesn't have a snapshot yet, and it doesn't retry its request until long after the current epoch is over and the other node has already deleted that snapshot. The fact that that loop in create_checkpoint() takes so long is something that perhaps we could look into, but it's not an issue in practice with long epoch lengths, so it's not a super high priority thing that should be causing test failures.

Fix it by just deleting that test and modifying the test loop state sync test to get the same conditions where we have fewer accounts than shards so that one of them is empty. (Although it should be noted that with nightly features, the state won't actually be empty since there'll be BandwidthSchedulerState data in the shards without accounts)

[marcelo-gonzalez]

Not doing it here, but I think prob all of those tests in that file can be deleted in favor of testloop

[Longarithm]

Nice

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.84%. Comparing base (1a3382c) to head (a1343b4).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #12473      +/-   ##
==========================================
- Coverage   69.84%   69.84%   -0.01%     
==========================================
  Files         838      838              
  Lines      169385   169385              
  Branches   169385   169385              
==========================================
- Hits       118314   118313       -1     
- Misses      45819    45823       +4     
+ Partials     5252     5249       -3     

Flag	Coverage Δ
backward-compatibility	0.16% <ø> (ø)
db-migration	0.16% <ø> (ø)
genesis-check	1.29% <ø> (ø)
linux	69.15% <ø> (-0.02%)	⬇️
linux-nightly	69.43% <ø> (-0.01%)	⬇️
macos	51.04% <ø> (+0.02%)	⬆️
pytests	1.60% <ø> (ø)
sanity-checks	1.40% <ø> (ø)
unittests	69.67% <ø> (-0.01%)	⬇️
upgradability	0.21% <ø> (ø)

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