Fix reaction to rejected orbit command

[MaEtUgR]

Describe problem solved by this pull request
This is a follow-up to #19362 fixing an already previoulsly existing bug. Thanks to @mrivi for finding it!

When commanding a too large Orbit she got invalid setpoints. I figured out that’s because since the introduction the command handling for flight tasks (which is only used for orbit yet) switches to the most basic position mode flight task upon command parameter rejection.

Describe your solution

• Switch to the failsafe flight task when command parameters were not accepted.
  • This makes the drone just stop and wait for further actions.
  • This solves getting invalid setpoint messages when no RC is connected.
  • This also solves ending up in an "aggressive" position mode unexpectedly.
• Report "denied" instead of "failed" as the command result in the acknowledgment for invalid parameters because that matches the MAVLink definition see: https://mavlink.io/en/messages/common.html#MAV_RESULT
• Inform the user directly from the Orbit command processing when the radius exceeds the limit. This needs to be backward compatible with mavlink_log since AMC doesn't support events yet.
• Minor refactoring.

Test data / coverage
This was tested in simulation to solve the issue and result in an improved user experience because of the error message and the correct command result.

[MaEtUgR]

This exact patch was already reviewed by @ThomasDebrunner before.
The only question that came up is checking equality instead of bigger or equal on the error code and that's the same because the possible errors are zero or negative:

PX4-Autopilot/src/modules/flight_mode_manager/FlightModeManager.hpp

Lines 61 to 65 in 18074de

	enum class FlightTaskError : int {
	NoError = 0,
	InvalidTask = -1,
	ActivationFailed = -2
	};