[Improvement] improve the backup directory in object storage

[ldming]

Is your improvement request related to a problem? Please describe.

Now, I have a cluster named mysql-cluster in default namespace, and enable the cluster backup to S3, the backups directory in S3 is as follows:

s3://lc-test/pvc-479b1fce-7dc5-4125-9917-1e4c34e10a0b/default/mycluster-b143cb67-272f-4f8b-97ad-42ad0221e03d/mysql/b143cb67-mycluster-default-logfile/binlog_sentinel_005.json

The backup path should be distinguished according to the cluster, which is convenient for users to find and manage.