Refactor GitHub worflow for tests

[patrick91]

This PR:

• Removes our custom cache implementation in favour of setup-python's one (less code for us)
• moves the windows test to only one version of python (to make tests faster and simplify the setup)
• adds a new matrix for starlette
• moves pyright and mypy tests on a different job

[codecov]

Codecov Report

Merging #1913 (a6092b4) into main (1b85e0c) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #1913   +/-   ##
=======================================
  Coverage   98.04%   98.04%           
=======================================
  Files         143      143           
  Lines        5562     5562           
  Branches     1023     1023           
=======================================
  Hits         5453     5453           
  Misses         56       56           
  Partials       53       53           

[botberry]

Hi, thanks for contributing to Strawberry 🍓!

We noticed that this PR is missing a RELEASE.md file. We use that to automatically do releases here on GitHub and, most importantly, to PyPI!

So as soon as this PR is merged, a release will be made 🚀.

Here's an example of RELEASE.md:

Release type: patch

Description of the changes, ideally with some examples, if adding a new feature.

Release type can be one of patch, minor or major. We use semver, so make sure to pick the appropriate type. If in doubt feel free to ask :)

Here's the tweet text:

🆕 Release (next) is out! Thanks to @patrick91 for the PR 👏

Get it here 👉 https://github.com/strawberry-graphql/strawberry/releases/tag/(next)