fix: close CloseableIterable owners in Iceberg read paths

[mengw15]

What changes were proposed in this PR?

Fixes a resource leak in IcebergUtil.readDataFileAsIterator and five sibling sites in IcebergDocument that share the same anti-pattern:

closeableIterable.iterator().asScala

The bare Iterator returned to callers held no reference to its parent CloseableIterable, so the parent could never be closed. Under S3FileIO:

1. Every read leaked one S3InputStream (kept open until GC because nothing in the call graph could close it).
2. The leaked stream had already borrowed one slot from the AWS SDK's ApacheHttpClient connection pool (default 50; texera did not override).
3. After ~50 leaked reads the pool may saturate; new S3 reads then block on acquireConnection until JVM restart.

This PR:

• Introduces CloseableScalaIterator[T] (Iterator[T] with AutoCloseable, idempotent close()) in IcebergUtil, which wraps a CloseableIterable[T] and propagates close() to the parent.
• Changes IcebergUtil.readDataFileAsIterator to return CloseableScalaIterator[Record] instead of bare Iterator[Record]. Callers must now close it (e.g. via Using.resource).
• Updates the single caller in IcebergDocument's read iterator to track the close handle in a sibling AutoCloseable field (currentRecordIteratorCloser) and close it on file-switch, on exhaustion, and on caller-imposed until cap. The sibling field is necessary because Iterator.drop(n) returns a bare iterator that loses the wrapper type.
• Wraps the four eagerly-consumed planFiles() call sites — getCount, seekToUsableFile, getTableStatistics, asInputStream — in Using.resource so the metadata-side CloseableIterable<FileScanTask> is closed promptly.

Known limitation (out of scope here): if a caller of IcebergDocument.get() / getRange() / getAfter() stops iterating before hasNext returns false (e.g. throws mid-loop, or calls .take(n) and then drops the result), the LAST file's CloseableScalaIterator will leak until JVM GC. Fixing this requires changing the public Iterator[T] return type on VirtualDocument to Iterator[T] with AutoCloseable and updating all callers — best done as a separate refactor.

Any related issues, documentation, discussions?

Closes #5143.

How was this PR tested?

• Added IcebergUtilLeakSpec (2 cases): validates that CloseableScalaIterator (a) closes its parent CloseableIterable when used inside Using.resource, and (b) is idempotent under repeated close() calls.
• All existing iceberg specs still pass:
  • IcebergUtilSpec: 14/14
  • IcebergUtilLeakSpec: 2/2 (new)
  • IcebergDocumentSpec: 18/18 (exercises the modified read iterator's close-on-reassign / close-on-exhaustion paths against real Iceberg infrastructure)
  • IcebergTableStatsSpec: 12/12 (exercises getTableStatistics with the new Using.resource wrap)
  • IcebergDocumentConsoleMessagesSpec: 1/1

Run locally:

sbt "WorkflowCore/testOnly org.apache.texera.amber.util.IcebergUtilSpec org.apache.texera.amber.util.IcebergUtilLeakSpec org.apache.texera.amber.storage.result.iceberg.*"

Result: 47 succeeded, 0 failed.

Was this PR authored or co-authored using generative AI tooling?

Generated-by: Claude Code (claude-opus-4-7)

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 43.39%. Comparing base (bf2f92c) to head (31cbdff).

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #5149      +/-   ##
============================================
+ Coverage     43.36%   43.39%   +0.02%     
+ Complexity     2217     2214       -3     
============================================
  Files          1049     1049              
  Lines         40560    40569       +9     
  Branches       4322     4323       +1     
============================================
+ Hits          17589    17605      +16     
+ Misses        21883    21871      -12     
- Partials       1088     1093       +5     

Flag	Coverage Δ		*Carryforward flag
access-control-service	39.53% <ø> (ø)
agent-service	33.76% <ø> (ø)		Carriedforward from bf2f92c
amber	43.92% <100.00%> (+0.07%)	⬆️
computing-unit-managing-service	0.00% <ø> (ø)
config-service	0.00% <ø> (ø)
file-service	32.18% <ø> (ø)
frontend	34.61% <ø> (ø)		Carriedforward from bf2f92c
python	90.50% <ø> (ø)		Carriedforward from bf2f92c
workflow-compiling-service	56.81% <ø> (ø)

*This pull request uses carry forward flags. Click here to find out more.

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[Yicong-Huang]

Left comments in line. I think the direction is correct, I like the idea of using ClosableIterator! but the implementation can be improved.

Also please make sure coverage is filled.

[Yicong-Huang]

LGTM!