Module improvement tracking issue

This issue tracks improvements and missing features of submodules:

- Recipes can depend on recipes in parent or sibling modules
- Variables defined in one module can be referenced from another
- #2442
- #2271
- Allow submodules to load `.env` files
- #2119
- Make all errors, not just compilation errors, refer to module source file path as appropriate
- Make `just --show` work with modules
- #2629

This thread should probably be used for general discussion. If you're interested in one of the above features, mention it in this thread and I'll create a dedicated issue for it.