SCons: Integrate annotations where relevant

[Repiteo]

• Supersedes SCons: Integrate annotations as required import #99180

In hindsight, applying a static boilerplate to all Python files was far too excessive. It turns out there is full support for gradually integrating modern type-hint syntax via FA¹ instead. As such, this PR only integrates from __future__ import annotations on the files that can take immediate advantage of it:

# Before
from typing import List, Optional, Tuple, Union

def some_function(env: "ForwardDeclaredType") -> Optional[Tuple[List[str], Union[int, float]]]:

# After
from __future__ import annotations

def some_function(env: ForwardDeclaredType) -> tuple[list[str], int | float]] | None:

Footnotes

1. https://docs.astral.sh/ruff/rules/#flake8-future-annotations-fa ↩