[Snapshot V2] Integrate delete snapshot flow with pinned timestamp

[anshu1106]

Is your feature request related to a problem? Please describe

• The snapshots created with pinned timestamp need to unpin the timestamp at the time of deletion.
• The snapshots created with pinned timestamp doesn't write per shard snapshot metadata files for which LIST call at the time of cleanup in not needed
• The snapshots created with pinned timestamp doesn't have to explicitly cleanup lock files at the time of deletion.
  More details can be found in the RFC
• There is a separate issue to handle remote store file cleanup for deleted indices - [Snapshot V2] Add support for remote store files cleanup #15466

Related component

Storage:Snapshots

Describe alternatives you've considered

NA

Additional context

No response