ci: use the native libcst parser

[onerandomusername]

Summary

Use the native libcst parser. Its not yet compatiable with all 3.10 and 3.11 features (eg match statements and the new union format), but that's okay, as we're compatible with python 3.8 and so we don't use those features.

This should result in codemods being faster both locally and in ci.

Depending on when #958 is merged, a change will need to be made to add this environment to both codemods.

Checklist

• If code changes were made, then they have been tested
  • I have updated the documentation to reflect the changes
  • I have formatted the code properly by running pdm lint
  • I have type-checked the code by running pdm pyright
• This PR fixes an issue
• This PR adds something new (e.g. new method or parameters)
• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• This PR is not a code change (e.g. documentation, README, ...)

[shiftinv]

Why not set this globally, similar to PDM_IGNORE_SAVED_PYTHON?

[onerandomusername]

Why not set this globally, similar to PDM_IGNORE_SAVED_PYTHON?

somewhat updated in e77ebc4