Compass calibration screen does not remember last setting

On Rover, at least, the compass calibration screen does not remember (or understand) that "APM with External Compass" was selected. Instead, when you return to that screen after the calibration process it displays "Manual: ROTATION_ROLL 180", which is equivalent but confusing.

Reproduce the issue on Rover by selecting "APM with External Compass," completing calibration, and returning to the compass calibration screen. Trace the screen's setting-display and calibration-state handling; done means the previous selection is remembered and shown as "APM with External Compass" rather than the equivalent manual rotation.

Written by the indexing model from the issue text.