scripts: generate_rust_analyzer.py: add type hints

scripts: generate_rust_analyzer.py: add type hints

Python type hints allow static analysis tools like mypy to detect type
errors during development, improving the developer experience.

Python type hints have been present in the kernel since 2019 at the
latest; see commit 6ebf5866f2e8 ("kunit: tool: add Python wrappers for
running KUnit tests").

Add a subclass of `argparse.Namespace` to get type checking on the CLI
arguments.

Run `mypy --strict scripts/generate_rust_analyzer.py --python-version
3.9` to verify. Note that `mypy` no longer supports python < 3.9.

Tested-by: Daniel Almeida <daniel.almeida@collabora.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Reviewed-by: Trevor Gross <tmgross@umich.edu>
Reviewed-by: Jesung Yang <y.j3ms.n@gmail.com>
Tested-by: Jesung Yang <y.j3ms.n@gmail.com>
Link: https://patch.msgid.link/20260122-rust-analyzer-types-v1-3-29cc2e91dcd5@kernel.org
Signed-off-by: Tamir Duberstein <tamird@kernel.org>