Multi host settings API

[MjnMixael]

Setting as draft for now because I still need to wire up and test several of these methods.. but if someone more familiar with the multi code wanted to give it a preliminary look, that'd be helpful.

EDIT: I should add that I intentionally left voice settings out. They can be added once voice transmission is fully implemented again.

[MjnMixael]

Everything's tested and seems to work. Ready for review.

[notimaginative]

I should have probably done the reviews in the correct order, but I didn't. So I reviewed #6077 first and it just has most the same stuff here. Same issues too. So would you prefer that I redo those comments here, or can you sort that out?

[MjnMixael]

I should have probably done the reviews in the correct order, but I didn't. So I reviewed #6077 first and it just has most the same stuff here. Same issues too. So would you prefer that I redo those comments here, or can you sort that out?

No worries. I can sort that out.

[MjnMixael]

#6077 is identical to this PR but with some additional API code for Multi Sync so all of those requested changes have been applied here as well.

[MjnMixael]

#6077 includes all of this PR and then some so I'm just gonna close this one