s3tables: Extract resource owner and bucket extraction into helper method

Create extractResourceOwnerAndBucket() helper to consolidate the repeated pattern
of unmarshaling metadata and extracting bucket name from resource path. This
pattern was duplicated in handleTagResource, handleListTagsForResource, and
handleUntagResource. Update all three handlers to use the helper.

Also update remaining uses of getPrincipalFromRequest() (in handler_bucket_create,
handler_bucket_get_list_delete, handler_namespace) to use getAccountID() after
consolidating the two identical methods.

weed/s3api/s3tables/handler_bucket_create.go

@@ -15,7 +15,7 @@ import (
 func (h *S3TablesHandler) handleCreateTableBucket(w http.ResponseWriter, r *http.Request, filerClient FilerClient) error {
 	// Check permission
 	accountID := h.getAccountID(r)
-	principal := h.getPrincipalFromRequest(r)
+	principal := h.getAccountID(r)
 	if !CanCreateTableBucket(principal, accountID, "") {
 		h.writeError(w, http.StatusForbidden, ErrCodeAccessDenied, "not authorized to create table buckets")
 		return NewAuthError("CreateTableBucket", principal, "not authorized to create table buckets")