Expose delay parameter for Hold action in Companion Protocol

[dmrgn1991]

@postlund I realized that I forgot to add any way of exposing the delay parameter for the Hold action in Companion. In practice this means that the delay value is currently hard-coded and as a result the app I'm testing is still uncooperative. This minor change exposes the delay param to the public key methods so that the user can set longer holds. Sorry I didn't think of this sooner, it should have been in my initial PR for sure.

[postlund]

I have not added this before as I have not seen any direct need for it, but I do see a use case for it so it is ok to add. As all the methods are part of the external interface (as defined in interface.py), it's not as easy as just adding new arguments. You must update the interface, update the facade (facade.py) and make sure to add the argument to all other protocols as well. Preferably update the other protocols to support the delay too. Delay would only be applicable to hold and can have the default value of one second.

I suggest that you read up about relaying and the facade here:

https://pyatv.dev/internals/design#relaying

It should help you get going. It is also worth adding this to the documentation to help others knowing about this feature:

https://pyatv.dev/development/control/

[dmrgn1991]

Okay, that makes sense, and I should have realized this would be more involved. I'll look into this and try to provide a complete implementation. Thanks, as always.