fix: fix hummock snapshot release in batch local execution

[hzxa21]

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What's changed and what's your intention?

Prior to this PR, batch query in local execution mode will release the hummock snapshot before query execution, which can cause the read epoch to be expired when reading from state store during query execution.

This PR fixes the issue by releasing the hummock snapshot after query execution is completed. Note the this is different from what we did for batch query in distributed execution mode, in which the hummock snapshot is released immediately after all scan executors are scheduled before the completion of query execution. I think this is acceptable since batch query in local execution mode is supposed to be fast and shouldn't hold the hummock snapshot for too long.

Checklist

• I have written necessary rustdoc comments
  - [ ] I have added necessary unit tests and integration tests
• All checks passed in ./risedev check (or alias, ./risedev c)

Refer to a related PR or issue link (optional)

Fix #5711

[codecov]

Codecov Report

Merging #5971 (cd4412b) into main (5ffeccb) will decrease coverage by 0.00%.
The diff coverage is 31.25%.

@@            Coverage Diff             @@
##             main    #5971      +/-   ##
==========================================
- Coverage   74.58%   74.58%   -0.01%     
==========================================
  Files         924      924              
  Lines      147411   147420       +9     
==========================================
+ Hits       109943   109947       +4     
- Misses      37468    37473       +5     

Flag	Coverage Δ
rust	74.58% <31.25%> (-0.01%)	⬇️

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

Impacted Files	Coverage Δ
src/frontend/src/handler/query.rs	20.24% <0.00%> (ø)
src/frontend/src/scheduler/local.rs	0.00% <0.00%> (ø)
...frontend/src/scheduler/hummock_snapshot_manager.rs	61.35% <50.00%> (-0.34%)	⬇️
src/frontend/src/scheduler/distributed/query.rs	74.87% <100.00%> (+0.06%)	⬆️

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[BugenZhao]

Good catch! LGTM