[Searchable Snapshots] Implement mechanism to specify cache path (API/setting definition/moving cache)

[kotwanikunal]

Is your feature request related to a problem? Please describe.
The feature request is a part of the overall file caching requirements needed for searchable snapshots.
As an user of searchable snapshots, I should be able to define a custom path for the cache.
Refer to #4964 for further details.

Describe alternatives you've considered
N/A

Additional context

• [Searchable Snapshot] Design file caching mechanism for block based files #4964

[xuezhou25]

This issue need more discussion because it maybe complex to implement cache moving.

For define the cache path through setting,
Currently, the cache directory is created in this class createRemoteSnapshotDirectoryFromSnapshot
right now, we use same path of shard path for caching

OpenSearch/server/src/main/java/org/opensearch/index/store/remote/directory/RemoteSnapshotDirectoryFactory.java

Lines 68 to 76 in c95a6b9

	final BlobPath blobPath = new BlobPath().add("indices")
	.add(IndexSettings.SEARCHABLE_SNAPSHOT_INDEX_ID.get(indexSettings.getSettings()))
	.add(Integer.toString(localShardPath.getShardId().getId()));
	final SnapshotId snapshotId = new SnapshotId(
	IndexSettings.SEARCHABLE_SNAPSHOT_ID_NAME.get(indexSettings.getSettings()),
	IndexSettings.SEARCHABLE_SNAPSHOT_ID_UUID.get(indexSettings.getSettings())
	);
	Path localStorePath = localShardPath.getDataPath().resolve(LOCAL_STORE_LOCATION);
	FSDirectory localStoreDir = FSDirectory.open(Files.createDirectories(localStorePath));

To make this configurable, there is a similar function for user to define custom path through setting like this

OpenSearch/server/src/main/java/org/opensearch/env/Environment.java

Line 69 in 4fc5c8d

public static final Setting<List<String>> PATH_DATA_SETTING = Setting.listSetting(

and then the new defined logic can be used in this class createRemoteSnapshotDirectoryFromSnapshot

Thanks @aabukhalil for his opinion.