[DOC] Update Create Snapshot API documentation with Snapshot Interoperability w/ Remote Store related changes

[harishbhakuni]

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Create Snapshot API Response Fields: https://opensearch.org/docs/latest/api-reference/snapshots/create-snapshot/#response-fields

With Snapshot Interoperability Feature, we will have a new field in Create Snapshot API response which will determine if a snapshot was shallow copy or full copy.

Field	Data type	Description
remote_store_index_shallow_copy	boolean	Whether current snapshot is full copy or shallow copy.

What other resources are available? Provide links to related issues, POCs, steps for testing, etc.

Related PR for code changes: opensearch-project/OpenSearch#7118
Design Document: opensearch-project/OpenSearch#6575

changes for this feature are already in 2.9 behind remote store experimental flag. to test, first bring up the opensearch node with 2.9 version, enable remote store feature. Update Repository setting with new flag as mentioned in #4598 and then a new snapshot response should have flag remote_store_index_shallow_copy as true.

Sample Response

curl -X PUT "localhost:9200/_snapshot/fullCopyRepository/full_snap10?wait_for_completion=true&pretty"
{
  "snapshot" : {
    "snapshot" : "full_snap",
    "uuid" : "06fAWrFURQmijsKJlSuNcg",
    "version_id" : 137217827,
    "version" : "3.0.0",
    "remote_store_index_shallow_copy" : false,
    "indices" : [
      "testidx-rs"
    ],
    "data_streams" : [ ],
    "include_global_state" : true,
    "state" : "SUCCESS",
    "start_time" : "2023-07-11T04:21:26.754Z",
    "start_time_in_millis" : 1689049286754,
    "end_time" : "2023-07-11T04:21:26.754Z",
    "end_time_in_millis" : 1689049286754,
    "duration_in_millis" : 0,
    "failures" : [ ],
    "shards" : {
      "total" : 5,
      "failed" : 0,
      "successful" : 5
    }
  }
}