feat(s3): stub bucket configuration list endpoints (#9571)

* feat(s3): stub bucket configuration list endpoints

Adds Get and List handlers for Analytics, Inventory, IntelligentTiering,
and Metrics bucket configurations. List returns an empty result with
IsTruncated=false; single-get returns NoSuchConfiguration so SDK error
parsing remains predictable.

* review: gate stubs on bucket existence

All eight stub handlers now call checkBucket via stubBucketGuard so
NoSuchBucket takes precedence over NoSuchConfiguration / empty-list
responses, matching AWS S3 precedence. Tests provide a cached bucket
so the guard sees it as present.

weed/s3api/s3err/s3api_errors.go

@@ -149,6 +149,8 @@ const (
 
 	// Object key length errors
 	ErrKeyTooLongError
+
+	ErrNoSuchConfiguration
 )
 
 // Error message constants for checksum validation
@@ -623,6 +625,12 @@ var errorCodeResponse = map[ErrorCode]APIError{
 		Description:    "Your key is too long.",
 		HTTPStatusCode: http.StatusBadRequest,
 	},
+
+	ErrNoSuchConfiguration: {
+		Code:           "NoSuchConfiguration",
+		Description:    "The specified configuration does not exist.",
+		HTTPStatusCode: http.StatusNotFound,
+	},
 }
 
 // GetAPIError provides API Error for input API error code.