Add annotation to preserve old encryption key

[Jorres]

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the new behavior?

Allows to specify a new annotation on the Database: ydb.tech/encryption-key-storage-name that will accept a Storage name override. Useful when a Storage object needs to be migrated (e.g. dev-storage-bad-name -> storage-standard-name to standardize internal Service endpoints generated by operator), but if we simply change .spec.StorageClusterRef, operator would recalculate key ID and database won't launch on next startup.

Other information

[Jorres]

Maybe, as an additional precaution, also save current storageNameRef in "status" and validate that it can also be changed if annotation is supplied