refactor: use versioned index for index file

[discord9]

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What's changed and what's your intention?

as title, use versioned index for index file, so rebuild index file can be easier to track

PR Checklist

Please convert it to a draft if some of the following conditions are not met.

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR requires documentation updates.
• API changes are backward compatible.
• Schema or data changes are backward compatible.

[Copilot]

Pull request overview

This PR refactors the index file system from using separate index_file_id fields to using versioned indexes with an index_version field. The main change replaces index_file_id: Option<String> with index_version: u64 in ManifestSstEntry, and introduces a new RegionIndexId type that combines file ID with version number.

Key Changes

• Replaced index_file_id: Option<FileId> with index_version: u64 in FileMeta and ManifestSstEntry
• Added RegionIndexId struct combining RegionFileId and version
• Updated index file path generation to support versioned filenames: {file_id}.{version}.puffin
• Modified FileType::Puffin to include version field

Reviewed changes

Copilot reviewed 38 out of 38 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
src/store-api/src/sst_entry.rs	Changed ManifestSstEntry to use index_version instead of index_file_id
src/mito2/src/sst/file.rs	Added RegionIndexId struct, updated FileMeta and FileHandle methods
src/mito2/src/sst/location.rs	Added versioned index file path functions and parsing logic
src/mito2/src/cache/file_cache.rs	Updated FileType::Puffin to include version field
src/mito2/src/sst/index.rs	Added index_version field to Indexer, updated IndexOutput
src/mito2/src/region/opener.rs	Updated cache loading to use versioned index keys
src/mito2/src/gc.rs	Updated GC worker (with known limitation for version support)
src/mito2/src/access_layer.rs	Added build_index_file_path_with_version to FilePathProvider trait
Multiple test files	Updated test utilities and expected values for new field
Multiple index files	Updated index appliers and creators to use RegionIndexId

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