Added support alternative names (designations) for exoplanets

[alex-w]

Description

This patch added support alternative names (designations) for exoplanets

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

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

[gzotti]

Please use a more expectable variable and key name, e.g. starAltName or starAliasName, everywhere.
If you think this is really needed, it else seems OK.

[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