[Remote Store] Avoid repeated delete calls for the stale segment files

[sachinpkale]

• Currently, we trigger cleanup of stale segment files from remote segment store on each flush.
• This clean-up is based on metadata file which references to the segment file
• If multiple stale segment metadata files refer to the same segment file, we call remoteDataDirectory.deleteFile multiple times.
• Functionally, this is a no-op as RemoteDirectory internally calls blobContainer.deleteBlobsIgnoringIfNotExists.
• But this can still make a call to the remote store which is un-necessary.
• We need to keep track of deleted files and avoid calling delete on the same deleted file.