feat: add PrivilegeImportBinlog object privilege

Binlog import (import option backup=true) and L0 import read Milvus's own
internal storage layout rather than a caller staging area, which is outside
the target collection's namespace. Add a cluster-level privilege so that
capability can be authorized separately from the collection-level Import
privilege.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Signed-off-by: bigsheeper <yihao.dai@zilliz.com>

Author: bigsheeper

go-api/commonpb/common.pb.go

@@ -525,6 +525,7 @@ enum ObjectPrivilege {
     PrivilegeSkipRLS = 91;
     PrivilegeViewRLS = 92;
     PrivilegeManageRLS = 93;
+    PrivilegeImportBinlog = 94;
 }
 
 message PrivilegeExt {