fix: S3 versioning memory leak in ListObjectVersions pagination (#7813)

* 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

weed/s3api/filer_multipart.go

@@ -360,12 +360,14 @@ func (s3a *S3ApiServer) completeMultipartUpload(r *http.Request, input *s3.Compl
 	// Check if versioning is configured for this bucket BEFORE creating any files
 	versioningState, vErr := s3a.getVersioningState(*input.Bucket)
 	if vErr == nil && versioningState == s3_constants.VersioningEnabled {
-		// For versioned buckets, create a version and return the version ID
-		versionId := generateVersionId()
+		// Use full object key (not just entryName) to ensure correct .versions directory is checked
+		normalizedKey := strings.TrimPrefix(*input.Key, "/")
+		useInvertedFormat := s3a.getVersionIdFormat(*input.Bucket, normalizedKey)
+		versionId := generateVersionId(useInvertedFormat)
 		versionFileName := s3a.getVersionFileName(versionId)
 		versionDir := dirName + "/" + entryName + s3_constants.VersionsFolder
 
-		// Move the completed object to the versions directory
+		// Create the version file in the .versions directory
 		err = s3a.mkFile(versionDir, versionFileName, finalParts, func(versionEntry *filer_pb.Entry) {
 			if versionEntry.Extended == nil {
 				versionEntry.Extended = make(map[string][]byte)