Clean task doesn't have access to build configuration/code

[Xymanek]

The clean task is currently a separate script, which is already problematic:

• 56 isn't applied to cleaning logic

• clean_cooker_output.ps1 had to be a separate file (it's called from both clean and build) and duplicates logic from build: https://github.com/X2CommunityCore/X2ModBuildCommon/blob/9c8172280b5545a4030ebfe9e6744b362b4a146d/clean_cooker_output.ps1#L6-L8
• clean.ps1 is forced to use some flaky logic due to lack of access to project's ContentOptions.json https://github.com/X2CommunityCore/X2ModBuildCommon/blob/9c8172280b5545a4030ebfe9e6744b362b4a146d/clean.ps1#L22-L24

Fixing this however requires significantly changing how individual projects consume X2MBC (and some internal refactor of X2MBC)

cc @robojumper