Feature request: Allow param to be fetched on background on "connect"

The problem is that sometimes you're in urgency having to do some action over telemetry connection, changing mode, reboot, whatever but "Getting params" window is blocking you. On mavproxy you can run commands as soon as the connection is etablished, while params are being fetched in background.
I think MP does the same too, while more vehicles are added to the same connection.

No files, tests, or entry points are named. Start by tracing connection establishment, parameter fetching, and the blocking "Getting params" window; done means commands can run immediately after connection while parameter retrieval continues in the background.

Written by the indexing model from the issue text.