feat: Allow imports of function definitions and aliased imports

[mark-koch]

Closes #425 and closes #427 and closes #134

• Allow importing of function definitions (before we could only import declarations)
• Until we have Hugr linking, we just lower everything into the same Hugr. This requires some changes to the compilation logic:
  • Differentiate between checking (module.check()) and full Hugr compilation (module.compile()) of modules
  • Importing modules only checks them
  • Hugr lowering is done at the end in one step over all imported modules
• Allow to import individual definitions instead of whole modules
• Allow aliased imports using kwargs (see test examples)

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 92.30769% with 6 lines in your changes missing coverage. Please review.

Project coverage is 92.53%. Comparing base (d5a1b6f) to head (d5236a1).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
guppylang/module.py	91.66%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #432      +/-   ##
==========================================
+ Coverage   92.48%   92.53%   +0.04%     
==========================================
  Files          48       48              
  Lines        5178     5249      +71     
==========================================
+ Hits         4789     4857      +68     
- Misses        389      392       +3     

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[mark-koch]

This is a bit annyoing. The qubit type now needs to be a Definition so we can import it, however Pythons Callable checks that the generic args are types at runtime...

Fixing this with a string annotation for now, but should figure out something better. See #433

[croyzor]

Nice!