Live's internal MIDI batching was causing sysex messages (i.e. to transition back to
hosted mode) to be sent before the background mode program change.

Also update the test framework to validate received messages more aggressively.

Adds `hardware.standalone = False` (if necessary) as part of the mode definition for
user-facing modes.

- adds an unmanaged (`None`) state for the device standalone status, and set it when the
device is in disabled mode
- always pass through disabled mode when receiving an identity response from the
controller (avoids potential failures to update devices that were quickly disconnected
and reconnected)
- when entering standalone modes, only send the standalone sysex if standalone mode
isn't already enabled

- More improvements to stabilization logic (add a separate initial vs stability delay)
- Respond to multiple identity requests from Live

- Add a `Device` class which manages the active mido I/O port
- Remove `loop` fixture and migrate to more native async methods
- Add `janus` for the thread-safe asyncio queue, replacing the manual poll approach
- Various cleanup for the internal test API

The timeout behavior was needlessly complicated given the device always needs to be
fully reinitialized (i.e. sent through standalone init mode) on port changes (since we
don't know which ports are changing), defeating the purpose of trying to keep it
responsive when other devices are connected/disconnected.