Quadplane transition failed(timed out), when airspeed use disabled.

If there was a previous discussion in the forum, link to it
https://discuss.ardupilot.org/t/quadplane-transition-failed-timed-out-where-is-airspeed-estimate/102393/1

## Bug report

**Issue details**
For log, please see forum post.
in short: ARSPD_USE was 0 due to upgrade, the plane was to autolearn it during flight.
The transition to plane failed/timed out, apparently due to missing AS?
I believe there is no fallback to inertia/GNSS speed in transition requirements?

**Version**
AP4.3.5

**Platform**
[ ] All
[ ] AntennaTracker
[ ] Copter
[x ] Plane
[ ] Rover
[ ] Submarine

**Airframe type**
Quadplane

**Hardware type**
Cube Orange

**Logs**
See linked forum post.

Start with the linked forum discussion and flight log to reproduce the QuadPlane transition timeout with ARSPD_USE set to 0. Trace the transition requirements and speed-estimate handling, then verify that the reported scenario completes according to the intended behavior and add or update coverage if the relevant test entry point is found.

Written by the indexing model from the issue text.