Improvements for type annotations

[The-Compiler]

• [x] Use Type Hinting Generics in Standard Collections (list, dict, type over typing.List etc.)
• [ ] Use from __future__ import annotations
  • [ ] Use PEP 604: New Type Union Operator, i.e. TheType | None instead of Optional[TheType]
  • [ ] Use "bare" annotations for forward declarations instead of stringified ones
  • [ ] Configure ruff to enforce from __future__ import annotations on every file for consistency
• [ ] Remove redundant type annotations from Sphinx docstrings (and possibly configure Sphinx to pick up the annotations, not sure what's needed for that nowadays)

Originally posted by @The-Compiler in https://github.com/pytest-dev/pytest-qt/pull/605#pullrequestreview-2937905480