[Feature Request] Optimise clone operation for incremental full cluster snapshots

[ashking94]

Is your feature request related to a problem? Please describe

During the development of shallow v1 snapshots, the clone operation code was modified to handle both shallow and existing full cluster incremental snapshots with the PR - #7496. However, in this PR, we have inadvertently introduced degraded experience for doc-rep cluster's clone snapshot operation where for each shard, there is dependency on repository data (index-N file for repository). If the index-N file size is above 512KB, then data needs to be downloaded from snapshot repository each time. This makes the clone snapshot operation slow. This can be reproduced by creating a lot of snapshots in a repo so that the index-N file size is above 512 KB.

Describe the solution you'd like

For doc-rep clusters, we don't need to depend on the repository data to decide which type of snapshot was taken. For docrep clusters, we only support full cluster incremental snapshots. In this case, we will check whether the cluster is remote store enabled or not, and if not, then directly jump to the part of cloning without seeking the repository data for any shard.

Related component

Storage:Snapshots

Describe alternatives you've considered

No response

Additional context

No response