* fix: S3 versioning memory leak in ListObjectVersions pagination
This commit fixes a memory leak issue in S3 versioning buckets where
ListObjectVersions with pagination (key-marker set) would collect ALL
versions in the bucket before filtering, causing O(N) memory usage.
Root cause:
- When keyMarker was set, maxCollect was set to 0 (unlimited)
- This caused findVersionsRecursively to traverse the entire bucket
- All versions were collected into memory, sorted, then filtered
Fix:
- Updated findVersionsRecursively to accept keyMarker and versionIdMarker
- Skips objects/versions before the marker during recursion (not after)
- Always respects maxCollect limit (never unlimited)
- Memory usage is now O(maxKeys) instead of O(total versions)
Refactoring:
- Introduced versionCollector struct to encapsulate collection state
- Extracted helper methods for cleaner, more testable code:
- matchesPrefixFilter: prefix matching logic
- shouldSkipObjectForMarker: keyMarker filtering
- shouldSkipVersionForMarker: versionIdMarker filtering
- processVersionsDirectory: .versions directory handling
- processExplicitDirectory: S3 directory object handling
- processRegularFile: pre-versioning file handling
- collectVersions: main recursive collection loop
- processDirectory: directory entry dispatch
This reduces the high QPS on 'find' and 'prefixList' operations
by skipping irrelevant objects during traversal.
Fixes customer-reported memory leak with high find/prefixList QPS
in Grafana for S3 versioning buckets.
* s3: infer version ID format from ExtLatestVersionIdKey metadata
Simplified version format detection:
- Removed ExtVersionIdFormatKey - no longer needed
- getVersionIdFormat() now infers format from ExtLatestVersionIdKey
- Uses isNewFormatVersionId() to check if latest version uses inverted format
This approach is simpler because:
- ExtLatestVersionIdKey is already stored in .versions directory metadata
- No need for separate format metadata field
- Format is naturally determined by the existing version IDs
