feat: support write for deletion vector

[lucasfang]

Purpose

Support write for deletion vectors by introducing a generic IndexFile base and implementing deletion-vector index file writing utilities, along with extending DeletionVector/BitmapDeletionVector serialization APIs and adding unit tests for bitmap deletion vectors.

Tests

BitmapDeletionVectorTest
DeletionVectorsIndexFileTest

API and Format

Documentation

[Copilot]

Pull request overview

This PR adds write-path support for deletion vectors by introducing a generic IndexFile base and implementing deletion-vector index file writing utilities, along with extending DeletionVector/BitmapDeletionVector serialization APIs and adding unit tests for bitmap deletion vectors.

Changes:

• Add IndexFile base abstraction (path/exists/size/delete) for index-file operations.
• Implement deletion vector index file writing (DeletionVectorsIndexFile, DeletionVectorIndexFileWriter, DeletionFileWriter).
• Extend DeletionVector / BitmapDeletionVector with cardinality + stream serialization and add BitmapDeletionVector unit tests.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
src/paimon/core/index/index_file.h	New base class for index-file filesystem/path operations
src/paimon/core/deletionvectors/deletion_vectors_index_file.h	Make DV index file derive from IndexFile and expose write entrypoint
src/paimon/core/deletionvectors/deletion_vectors_index_file.cpp	Implements DV index file write delegation to writer
src/paimon/core/deletionvectors/deletion_vector_index_file_writer.h	Declares DV index file writer (currently with unused target-size parameter)
src/paimon/core/deletionvectors/deletion_vector_index_file_writer.cpp	Implements writing a single DV file via DeletionFileWriter
src/paimon/core/deletionvectors/deletion_vector.h	Extends DV interface with GetCardinality() and SerializeTo(...)
src/paimon/core/deletionvectors/deletion_file_writer.h	New low-level writer producing IndexFileMeta + DV range metadata
src/paimon/core/deletionvectors/bitmap_deletion_vector.h	Refactors serialization declarations and adds constants
src/paimon/core/deletionvectors/bitmap_deletion_vector.cpp	Implements stream serialization + deserialize + bounds checking logic
src/paimon/core/deletionvectors/bitmap_deletion_vector_test.cpp	Adds unit tests for bitmap deletion vector behavior/serialization
src/paimon/CMakeLists.txt	Wires new sources and test into build

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[lxy-9602]

+1