Add initial implementation of a finalizer for the backup cleanup

[johscheuer]

Description

Fixes: #2357

Type of change

• New feature (non-breaking change which adds functionality)

Discussion

This is the first implementation approach to cleanup backups when the FoundationDBBackup resource is deleted and the according deletion policy is set (default is to keep everything running).

Testing

Ran an e2e test case with the policy.

Documentation

Updated the documentation.

Follow-up

[foundationdb-ci]

Result of fdb-kubernetes-operator-pr on Linux RHEL 9

• Commit ID: 776e628
• Duration 1:58:41
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)

[nicmorales9]

some nits but LGTM

[foundationdb-ci]

Result of fdb-kubernetes-operator-pr on Linux RHEL 9

• Commit ID: d61a01d
• Duration 2:12:58
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)

[foundationdb-ci]

Result of fdb-kubernetes-operator-pr on Linux RHEL 9

• Commit ID: e6055a0
• Duration 2:35:16
• Result: ❌ FAILED
• Error: Error while executing command: if $fail_test; then exit 1; fi. Reason: exit status 1
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)