Ensure exclusive access to radios per editorset

[kk7ds]

A ChirpLiveEditorSet represents a conversation with a single radio endpoint, but may involve multiple independent event streams. We really don't need multiple threads and queues for talking to a single radio, however radios with multiple sub-devices will end up with different Radio classes by nature. So, instead of collapsing editors into a single thread, we can just make them share a lock, established at the EditorSet level, which is what this patch does.

This also means the other drivers (that I know of) that do their own locking (kenwood_live, kenwood_d7, because settings) and ic9x (because multiple sub-devices) can simplify and rely on this being handled in the UI.

[kk7ds]

FYI @W8BSD this should make any threads for a single radio exclusive so we don't try to have more than one simultaneous conversation with the radio at a time. I've tested on a D700 for your new module, a TM-281 to confirm kenwood_live, and an IC-92 to get the other one. If you have a chance to look this over and/or test before we merge, that'd be cool. No rush since it's just cleanup.