Don't rename imported Main module that only imports names

[hubertp]

Pull Request Description

Turns that if you import a two-part import we had special code that would a) add Main submodule b) add an explicit rename.

b) is problematic because sometimes we only want to import specific names.
E.g.,

from Bar.Foo import Bar, Baz

would be translated to

from Bar.Foo.Main as Foo import Bar, Baz

and it should only be translated to

from Bar.Foo.Main import Bar, Baz

This change detects this scenario and does not add renames in that case.

Fixes 183276486.

Checklist

Please include the following checklist in your PR:

• The documentation has been updated if necessary.
• All code conforms to the
  Scala,
  Java,
  and
  Rust
  style guides.
• All code has been tested:
  • Unit tests have been written where possible.
  • If GUI codebase was changed: Enso GUI was tested when built using BOTH
    ./run ide build and ./run ide watch.

[hubertp]

@JaroslavTulach I don't think @kazcw needs to be aware of this one. This is added in a later compiler phase. Current parser gives correct IR.

[hubertp]

/cc @jdunkerley since you discovered it.

[JaroslavTulach]

Technical approval - I find the import system of Enso too confusing to judge what is right or wrong.

[radeusgd]

Btw. after we made it so that from X.Y import Z does not bring Y into scope, should we even keep the form from X.Y as W import Z? I assume that the explicit rename makes it bring the W into scope - but shouldn't we just make this form illegal? If you want to bring into scope, you should add a separate import import X.Y as W, and the from imports should be used only for importing symbols from within a scope - so that each import form would have only one responsibility.

[kazcw]

@radeusgd I'll be removing that syntax from the new parser, discussion here: #3710 (comment)