Generate operators in CI

Resolves #3 (closed).

Revamps our CI:

• Search for all operators-(.*)\.toml files automatically.
• Regenerate all operators from those files (deletes all generated code that was checked in).
• Add a manually triggered job to create an MR with the new changes and freshly generated code.

This greatly simplifies the development process as now, the operators must not be generated locally by the developer (which can be a quite lengthy process).

The implementation might seem a little complicated at first. We (I) want to automatically collect all toml files instead of listing them in the CI YAML, so that anyone can add or remove toml files without any extra thinking. Therefore, we need to start a parent job that walks the directory and creates a child pipeline for the actual generation.

I am not sure why the CI produced different code from what was already in the repository (for those three changed files). This could be a determinism issue in the generator.