MOD-7133: [Feature Request] Add FT.ALIASGET command

[alexander-schranz]

Is your feature request related to a problem? Please describe.

There is currently no way to read an alias only to create, update or delete.

Describe the solution you'd like

Add a new FT.ALIASGET <alias> command which returns not exist or the <index> name.

Describe alternatives you've considered

I need to additional write a key value store to have mapping from alias -> index name.

Additional context

Related a little bit to RedisJSON/RedisJSON#1197.

[github-actions]

This issue is stale because it has been open for 60 days with no activity.

[alexander-schranz]

Think this would still be a nice feature.