Replace black and flake8 with ruff for linting and formatting

- Remove .flake8; add [tool.ruff] and [tool.ruff.format] config in pyproject.toml
  (line-length 120, excludes, ignore list, per-file-ignores, mccabe complexity)
- Update GitHub workflow lint job to run `ruff check .` and `ruff format --check .`
- Swap black and flake8 for ruff in requirements.txt and Pipfile
- Change capnp/__init__.py to ruff-style noqa comment
- Move max-complexity into [tool.ruff.lint.mccabe], lint options into [tool.ruff.lint]
- Add per-file-ignores for capnp/__init__.py (F401, F403, F405), remove inline noqa
- Run ruff format across codebase (24 files) for consistent style

scripts/capnp_test_pycapnp.py

@@ -4,9 +4,7 @@ import sys
 
 import capnp
 
-capnp.add_import_hook(
-    [os.getcwd(), "/usr/local/include/"]
-)  # change this to be auto-detected?
+capnp.add_import_hook([os.getcwd(), "/usr/local/include/"])  # change this to be auto-detected?
 
 import test_capnp  # noqa: E402