Request for private file-scope modules in a package

[BryantLam]

Assuming #7847 or #8470 is resolved...

When I'm developing a Mason package, I want to be able to set a file-level module as private. You can do this today by simply creating a submodule with private module M { ... }, but I can't test that at the boundary of a package yet.

When #8470 is resolved, I imagine this feature request will just work, but I'll have to make an explicit top-level private module for my file-module. This is good enough for me because it's explicit in the code that the module is private, doesn't change anything in the compiler or Mason, and doesn't require compiler flags.

[aconsroe-hpe]

All the linked issues have been resolved at this point. Feel free to open a new issue if you still find something missing.