AstroCalc: show current location of object

[alex-w]

Description

This pull request adds the ability to show current locations of objects which already have computed ephemeris.

Fixes #2937 (issue)

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

How Has This Been Tested?

• Run Stellarium
• Open AstroCalc/Ephemeris tool and compute ephemeris
• Open "Extra options..." windows and mark "Show marker for current location"
• See the screen

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.

[github-actions]

Hello @alex-w!

Please check the fresh version (development snapshot) of Stellarium:
https://github.com/Stellarium/stellarium-data/releases/tag/weekly-snapshot

[github-actions]

Hello @alex-w!

Please check the latest stable version of Stellarium:
https://github.com/Stellarium/stellarium/releases/latest