Remove deprecated key_remapping and filter_join_indices APIs

[PointKernel]

Description

This PR removes the deprecated KEY_REMAP_BUILD_NULL, remap_build_keys, and remap_probe_keys key-remapping aliases and the deprecated filter_join_indices overload without output_size.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

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[PointKernel]

/ok to test 1bd1c81

[PointKernel]

/ok to test 9e9e371

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No actionable comments were generated in the recent review. 🎉

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📥 Commits

Reviewing files that changed from the base of the PR and between d466e60 and 9e9e371.

📒 Files selected for processing (3)

• cpp/include/cudf/join/join.hpp
• cpp/include/cudf/join/key_remapping.hpp
• cpp/src/join/filter_join_indices/filter_join_indices.cu

💤 Files with no reviewable changes (3)

• cpp/src/join/filter_join_indices/filter_join_indices.cu
• cpp/include/cudf/join/key_remapping.hpp
• cpp/include/cudf/join/join.hpp

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📝 Walkthrough

Summary by CodeRabbit

• API Updates
  • Updated filtered join index operations to accept an optional output-size limit.
  • Removed deprecated join key remapping aliases and methods; use the current right/left key remapping APIs instead.
  • Removed the deprecated filtered join overload in favor of the updated interface.

Walkthrough

Changes

Join API updates

Layer / File(s)	Summary
Filter join output sizing cpp/include/cudf/join/join.hpp, cpp/src/join/filter_join_indices/filter_join_indices.cu	filter_join_indices accepts an optional output_size and forwards it to the detail implementation.
Deprecated key remapping removal cpp/include/cudf/join/key_remapping.hpp	Removes KEY_REMAP_BUILD_NULL, remap_build_keys, and remap_probe_keys.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• rapidsai/cudf#23012: Introduces the related filter-join output-sizing flow.
• rapidsai/cudf#23395: Updates overlapping filter_join_indices APIs and output-sizing behavior.
• rapidsai/cudf#23398: Threads output_size through related filter-join APIs and call sites.

Suggested reviewers: mhaseeb123, bdice, vyasr

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the removal of deprecated key_remapping and filter_join_indices APIs.
Description check	✅ Passed	The description directly matches the changes by listing the removed deprecated aliases and overload.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

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[PointKernel]

/merge