Add `Container level WORM` immutable object support for Azure Blob Storage.

[renormalize]

What this PR does / why we need it:

Enables etcd-backup-restore to handle immutable objects as provided by Container Level WORM in Azure Blob Storage.

This PR mirrors #776 for Azure Blob Storage.

Which issue(s) this PR fixes: Fixes # #777 only for ABS.

Special notes for your reviewer:

The same conventions are followed as in #776. Please let me know if you find anything that doesn't stick to those conventions.

Release note:

etcd-backup-restore now supports immutable objects for storage provider: Azure Blob Storage, provided by the [Container Level WORM](hhttps://learn.microsoft.com/en-us/azure/storage/blobs/immutable-container-level-worm-policies) feature.

Snapshots garbage collection performed by etcd-backup-restore (if enabled) for ABS is performed only when the objects' immutability period expires.

Support for Container level WORM (ABS) in etcd-backup-restore is backward compatible. For more info please refer to this doc: https://github.com/gardener/etcd-backup-restore/blob/master/docs/usage/immutable_snapshots.md

[anveshreddy18]

/assign

[ishan16696]

Hi @renormalize , Can you please resolve the merge conflicts for this PR and get this PR merge ?

[renormalize]

@ishan16696 yes I'll get to it ASAP.

[renormalize]

Needs changes. Please do not merge.