Add some support for loading fake modules

[mrbean-bremen]

• works only if open_code patch mode is not off
• see Cannot import file from fakefs #1079

This will not handle all possible cases. Relative imports are not supported, and for absolute imports in dot notation an __init__.py is expected in module paths above the leaf module.

Tasks

• Unit tests added that reproduce the issue or prove feature is working
• Fix or feature added
• Entry to release notes added
• Pre-commit CI shows no errors
• Unit tests passing
• For documentation changes: The Read the Docs preview builds and looks as expected

[mrbean-bremen]

@Aran-Fey: I only added two tests (one of them basically your example test), please check if you need more cases covered.

[Aran-Fey]

I'm surprised that relative imports don't work, but that's not a problem for me. This will help a lot, thanks!

[mrbean-bremen]

I'm surprised that relative imports don't work

You are right, this is easy to fix. Will do this.