Script generator: Add manual test for standalone script generator (VM not a good solution)

As a user I want to be able to use the script generator standalone, without having to worry about installing git or python. The standalone script generator is designed to be used in this way, packaging git and python with it. Every release we should verify that this reqirement is fulfilled by running a system test, possibly manually using a blank VM.

## Acceptance criteria
- [ ] The standalone script generator is tested every release for its lack of dependence on preinstalled third-party software

## Notes

#5700 was an issue which could have been caught by such a test

Start with the standalone script generator and the release process; the issue names no specific files or existing test entry point. Define a repeatable system test in an environment without preinstalled Git or Python, then run it for each release. Done means the generator is verified to run without those third-party dependencies and the procedure is recorded.

Scritto dal modello di indicizzazione a partire dal testo della issue.