feat: mod.nr entrypoint

[michaeljklein]

Description

Problem*

Resolves #4860

Summary*

Allow using mod.nr as the entrypoint to a module.

Additional Context

I expected find_module to have the logic for this, but after a bunch of debugging, it seems somehow unrelated. I.e. it's not even called for the mod.nr case.

Documentation*

Check one:

• No documentation needed.
• Documentation included in this PR.
• [For Experimental Features] Documentation to be submitted in a separate PR.

PR Checklist*

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.