Meridian flips handled by Mount

Summary:
Currently, meridian flips are controlled by the capture module. This has the limitation, that meridian flips
can only be issued if capturing is running. If the mount is tracking a position without capturing running,
no meridian flip will take place.

With this proposal, the mount controls meridian flips. As soon as the meridian flip limit is reached,
it requests a meridian flip from the capture module. In case that a frame capturing is running, the
meridian flip is delayed until the frame has been captured.

If capturing is not running, the meridian flip is started immediately.

Test Plan:

1. Test without capturing
   • Slew to a position east, but close to the meridian.
   • Select the meridian flip checkbox on the Mount tab.
   • Expected result: meridian flip executed as soon as the position crosses the meridian.

2. Test with capturing
   • Create an imaging sequence with meridian flip enabled.
   • Slew to a position east, but close to the meridian.
   • Start the imaging sequence.
   • Wait, until the position crosses the meridian.
   • Expected result: meridian flip executed, image sequence interrupted and continued after meridian flip.

3. Test with scheduled capturing
   • Create an imaging sequence with meridian flip enabled.
   • Create a schedule using this sequence and a target east, but close to the meridian.
   • Start the schedule.
   • Expected result: meridian flip executed and schedule continues afterwards.

4. Meridian flip during paused imaging session
   • Similar as 2., but pause the imaging session before the meridian has been reached.
   • Expected result: meridian flip executed, imaging session remains paused.

5. No meridian flip when mount is not tracking
   • Create an imaging sequence with meridian flip enabled.
   • Slew to a position east, but close to the meridian.
   • Start the imaging sequence.
   • Stop tracking.
   • Expected result: imaging sequence continues, no meridian flip happens
   • Extension: start tracking again
   • Expected result: meridian flip will be executed as soon as the next frame is complete.
   • Extension: park mount
   • Expected result: no meridian flip executed, imaging session continues.

Reviewers: mutlaqja, TallFurryMan, alainz

Reviewed By: mutlaqja

Subscribers: kde-edu

Tags: KDE Edu

Differential Revision: https://phabricator.kde.org/D18235