Guided mode problems

[DonLakeFlyer]

Related to discussion here #12536.

A couple issues that remain (neither of them is a consequence of this PR, but maybe they should be fixed here) are:

• At least in ArduPilot, when launching the Go To action while in Auto mode, the action's hide trigger quickly toggles, not sure why. The action still happens normally, but its cancel handler is called when it shouldn't. This makes the Go here map item disappear.
• When the Go To action fails after confirmation (for example, when the destination is too far) the map item doesn't reflect this (it remains at the confirmed position).
• On the loiter radius saving, what you say makes me think that in general preserving the loiter radius as a setting across runs, vehicles, flights is probably a bad thing in general. It should be removed.