Use an ID for planets for faster comparison

[gzotti]

EXPERIMENTAL DRAFT, ignore!

VTune indicates that a considerable percentage of frame time is string comparison in the solar system, i.e., comparing englishName. This branch tries to mitigate the situation, first by using a hash-based ID.

Description

Fixes # (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
• Housekeeping

How Has This Been Tested?

Test Configuration:

• Operating system: Windows 11
• Graphics Card: 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.

[github-actions]

Hello @gzotti!

Thank you for the suggested improvement.

[alex-w]

How many objects in your ssystem.ini files and how many increases performance?

[gzotti]

I have started editing about 2 hours ago and wrote "EXPERIMENTAL DRAFT, ignore!" above. If VTune was right, 15-20% of SolarSystem::draw() goes into string equality tests with a solar system of around 11.000 objects.
Another repeated call seems to be getSolarEclipseFactor which is called in SolarSystem::draw and then in each Planet::draw. And StelCore::getProjection is also called twice, but I have not checked yet where and whether these are same-named overloads. In the best case, their results could be re-used.

[github-actions]

Conflicts have been resolved. A maintainer will review the pull request shortly.