Proposal: deprecate support for legacy type hinting functionality, i.e. [float] instead of list[float], {str: int} instead of dict[str,int], etc

[ptomecek]

Is your feature request related to a problem? Please describe.
Simplify the existing codebase and make performance improvements during graph parsing/type checking/building. These files would no longer be necessary:

• container_type_normalizer.py
• type_annotation_normalizer_transformer.py

Describe the solution you'd like
Add deprecation messages to use of the legacy container types, followed by complete removal down the road.

Describe alternatives you've considered
Leaving the functionality in.

Additional context
Now that python type hints are standardized and ubiquitous, it doesn't make so much sense to support syntax that was developed long ago.

[AdamGlustein]

Since type hinting for generic containers (i.e. list[int]) only became supported by the Python parser in 3.9, I think we could only do this if we drop support for 3.8. We would at least need to maintain support for typing.List and other collections.

[timkpaine]

Python 3.8 is end of life very soon anyway https://devguide.python.org/versions/

[ptomecek]

To be clear, I think typing.List[float] should be supported on Python 3.8+ and list[float] on 3.9+. I don't think [float] should be supported at all, because it's not standard typing syntax. So the only things I think we should get rid of are the ones that aren't valid type hints for any version of python.

[timkpaine]

agreed on that, no reason to make up conventions when the existing mechanisms are sufficient