fix: avoid file purge when they are used in queries

[jiacai2050]

Which issue does this PR close?

Closes #427 #534

Rationale for this change

What changes are included in this PR?

• Hold sst reference in merge/chain iterator, so sst cannot be pushed to purge queue when there are queries.

Are there any user-facing changes?

No

How does this change test

CI

[codecov-commenter]

Codecov Report

Merging #699 (253b4d0) into main (f79890b) will increase coverage by 0.82%.
The diff coverage is 88.88%.

❗ Current head 253b4d0 differs from pull request most recent head 6d366f2. Consider uploading reports for the commit 6d366f2 to get more accurate results

@@            Coverage Diff             @@
##             main     #699      +/-   ##
==========================================
+ Coverage   67.55%   68.38%   +0.82%     
==========================================
  Files         281      281              
  Lines       44343    44351       +8     
==========================================
+ Hits        29956    30328     +372     
+ Misses      14387    14023     -364     

Impacted Files	Coverage Δ
analytic_engine/src/row_iter/chain.rs	56.56% <50.00%> (-0.06%)	⬇️
analytic_engine/src/row_iter/merge.rs	89.63% <100.00%> (+0.62%)	⬆️
analytic_engine/src/sst/file.rs	87.36% <100.00%> (+10.19%)	⬆️
components/skiplist/src/list.rs	98.87% <0.00%> (-0.23%)	⬇️
analytic_engine/src/setup.rs	56.63% <0.00%> (+0.32%)	⬆️
analytic_engine/src/table/version.rs	94.27% <0.00%> (+0.58%)	⬆️
analytic_engine/src/compaction/mod.rs	83.45% <0.00%> (+1.40%)	⬆️
analytic_engine/src/compaction/scheduler.rs	70.44% <0.00%> (+2.35%)	⬆️
analytic_engine/src/sst/parquet/meta_data.rs	90.90% <0.00%> (+3.55%)	⬆️
... and 10 more

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[ShiKaiWi]

LGTM