Enforce tags from extensions.blender.org with support for using an
alternate set of tags (for other repositories), or no tag validation
at all if the repositories choose not to enforce this.
- By default building & validating an extensions fails when unknown
tags are used.
- The option `--valid-tags`` has been added which can either:
- Reference a JSON file which lists valid tags per extension type.
- Pass in an empty string to disable tag validation.
Default to constraining packages to use Blender's official tags as every
extension defining their own tags is likely to result in many similar
tags & a bad user experience. Details in code-comments.
Implements #123986.
e3457bccbf