fix(spark): make export_instants descending order work

[yihua]

Describe the issue this Pull Request addresses

export_instants(..., desc => true) throws UnsupportedOperationException on every invocation. ExportInstantsProcedure builds its instant and file-status lists via asJava over immutable Scala collections, producing read-only java.util.Lists. The desc branch then reverses them in place with Collections.reverse, which calls List.set and fails on a read-only list. So descending export has never worked.

Summary and Changelog

• Wrap both nonArchivedInstants and archivedStatuses in a mutable new java.util.ArrayList(...) so Collections.reverse succeeds. Ascending export is unaffected.
• Add TestExportInstantsProcedure coverage: ascending export, the descending-order regression case (which fails without this fix), action filtering, and the invalid-local-folder error path.

Impact

Fixes export_instants with desc => true. No change to ascending behavior or other procedures.

Risk Level

low. One-line-per-list change from an immutable wrapper to a mutable copy; the descending regression test exercises the previously-broken path.

Documentation Update

none

Contributor's checklist

• Read through contributor's guide
• Enough context is provided in the sections above
• Adequate tests were added if applicable

[hudi-agent]

⚠️ 🤖 This review was generated by an AI agent and may contain mistakes. Please verify any suggestions before applying.

Thanks for the contribution! This PR fixes export_instants(..., desc => true), which previously always threw UnsupportedOperationException because Collections.reverse was called on read-only lists produced by asJava over immutable Scala collections; it now wraps both the instant and archive-status lists in mutable ArrayLists and adds regression test coverage. No issues flagged from this automated pass — a Hudi committer or PMC member can take it from here for a final review.

cc @yihua

[hudi-agent]

⚠️ 🤖 This review was generated by an AI agent and may contain mistakes. Please verify any suggestions before applying.

Thanks for working on this! This PR fixes export_instants(..., desc => true), which previously threw UnsupportedOperationException because Collections.reverse was called on read-only lists produced by asJava over immutable Scala collections. Wrapping both nonArchivedInstants and archivedStatuses in mutable ArrayList copies resolves the issue, and the ascending path is unaffected. No issues flagged from this automated pass — a Hudi committer or PMC member can take it from here for a final review.

cc @yihua

[hudi-bot]

CI report:

• ec33b4d Azure: SUCCESS

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