Allow number entities to be used as volume control for players

[alexbarcelo]

I see that both switch and media_players can be used as the "power" and "mute" controls of a Music Assistant "player".

I have some integrations that use a entity type of number to control the volume of a physical speaker, and I believe that it makes sense to allow that setup for Music Assistant players (given that arbitrary switches can already be used as entities that Music Assistant link to a player for controlling mute and power).

Does that make sense? It should not break anything and seems an interesting use case, right?