Update typing to Python 3.10 style

[dekkers]

Changes

This updates typing to the new Python 3.10 style. It also enables the ruff rules that check for this.

Almost all of the changes in this PR have been made by ruff. There were few places that ruff gave an error and couldn't fix it that I had to do by hand.

This only changes typing to things that are syntatically different but the same thing, so it shouldn't have any impact. It might still be good to do QA to make sure everything work correctly, especially because pydantic and FastAPI also do runtime things with types.

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Checklist for code reviewers:

Copy-paste the checklist from the docs/source/templates folder into your comment.

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Checklist for QA:

Copy-paste the checklist from the docs/source/templates folder into your comment.

[ammar92]

Checklist for QA:

• I have checked out this branch, and successfully ran a fresh make reset.
• I confirmed that there are no unintended functional regressions in this branch:
  • I have managed to pass the onboarding flow
  • Objects and Findings are created properly
  • Tasks are created and completed properly
• I confirmed that the PR's advertised feature or hotfix works as intended.

What works:

Seems to work as usual.