[Feature] Support Backup/Restore for external catalog

[srlch]

• [Feature] Support Backup/Restore for external catalog #52895
  In this PR, we support Backup/Restore for External Catalog. User can Backup All of or part of
  External Catalog metadata into snapshot file and restore it into a new cluster.

The following summarizes the behavioral changes caused by this PR:

1. New syntax to support Backup/Restore for External Catalog, here is the new part for it:

BACKUP (ALL EXTERNAL CATALOGS | EXTERNAL CATALOG <catalog_name> [, ...]) SNAPSHOT <snapshot_name>
TO <repo_name> [PROPERTIES]

RESTORE SNAPSHOT <snapshot_name> FROM <repo_name>
[ ALL EXTERNAL CATALOGS | EXTERNAL CATALOG <catalog_name> AS <alias> [, ...] ]
[PROPERTIES]

CANCEL EXTERNAL CATALOG BACKUP

CANCEL EXTERNAL CATALOG RESTORE

2. For EXTERNAL CATALOG Backup/Restore, no db info and ON clause can be specified.
3. Only one Backup/Restore job can be executed at the same time in the cluster.