Allow Renaming of an Index from Source to Target with Transformations

[peternied]

Description

Indices cannot easily be renamed once they have been created. Migrations are one of the few opportunities to change the index name, it would be useful if this was supported.

What solution would you like?

When selecting indices for migration if source->target names could be specified this would allow for updating naming decisions that were made when the index was created but should be revisited.

[sumobrian]

This will be enabled with https://opensearch.atlassian.net/browse/MIGRATIONS-2146 and https://opensearch.atlassian.net/browse/MIGRATIONS-2152