[K8SPSMDB-801] Add support for PITR retention

[spron-in]

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Tell us about the feature

Currently PiTR files are not deleted during psmdb-backup deletion and there is no related command.

Normally this is could be done with pbm delete-pitr command: https://docs.percona.com/percona-backup-mongodb/pbm-commands.html#pbm-delete-pitr

kubectl -n psmdb exec -it my-cluster-name-rs0-0 -c backup-agent -- pbm --mongodb-uri="backup:UtwVhc6UKMXl1MHHS@my-cluster-name-rs0-0/admin?replicaSet=rs0&ssl=false" delete-pitr --older-than='2022-10-18T17:06:25'

But it will be great to specify how many days to keep pitr or delete it in pair with related full backups

Link to JIRA