Improvements for type annotations

[The-Compiler]

• 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 #605 (review)