Fix StelMovementMgr Zoomout

[gzotti]

Description

This should finally repair some mess around zoom-to-object, zoom in a bit more, zoom out a bit and zoom out to base view.
I had never seen this in operation given its default keyboard bindings that never worked on non-US keyboards, and some changes deemed relevant in 2022 may have broken the behaviour known and probably seen essential to others.
After explanations it becomes clear this is something of actual importance in a planetarium.

There are a few settings that are already involved in the whole workflow. However, maybe a LIFO stack of zoom states will be required for stepping in and out (with even more steps), with a master command to "zoom all the way to normal" scrubbing the stack.

This also makes another so-far hidden flag finally fully accessible: Pushing the view with the mouse cursor touching screen edge.

Fixes #3553

Screenshots (if appropriate):

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• This change requires a documentation update
• Housekeeping

How Has This Been Tested?

Test Configuration:

• Operating system: Windows 11
• Graphics Card: Geforce 3070Ti (but irrelevant)

Checklist:

• My code follows the code style of this project.
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (header file)
• I have updated the respective chapter in the Stellarium User Guide
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[github-actions]

Great PR! Please pay attention to the following items before merging:

Files matching src/**/*.cpp:

• Are possibly unused includes removed?

This is an automatically generated QA checklist based on modified files.