Make guiding more robust

Summary:
This diff contains several improvements to the Scheduler and Guiding modules:

1. Directly skip scheduler stage to capturing when guiding is already running. During the scheduler startup, the scheduler module recognizes if guiding is already running and directly jumps to capturing.
2. Recognizing settling errors and handle them as aborted guiding. When using PHD2 as guider, EKOS recognizes settling errors. They occur for example when no guiding star can be found during the attempt to start guiding.
3. Restart guiding with increasing delay. When a guiding problem occurs while starting the guiding, restarting guiding is delayed by an increasing delay.

Test Plan:
Ad 1: First start guiding and then start a scheduler job that requires guiding. Check if the job starts capturing. Without this diff, the scheduler hangs in the guiding stage.
Ad 2: Change the PHD2 exposure time to a very low value so that no guiding star can be found. Then start a scheduler job that requires guiding. Check if the scheduler tries to re-start guiding.
Ad 3: Similar as 2. Check if starting the guider is delayed by an increasing amount of time.

Reviewers: mutlaqja, TallFurryMan

Reviewed By: mutlaqja

Subscribers: kde-edu

Tags: KDE Edu

Differential Revision: https://phabricator.kde.org/D21739