* Add pre-commit config and GitHub Actions job
Contains the following hooks:
* buildifier - for formatting and linting Bazel files.
* mypy, ruff, isort, black - for Python typechecking, import hygiene,
static analysis, and formatting.
The pylint CI job was changed to be a pre-commit CI job, where pre-commit
is bootstrapped via Python.
Pylint is currently no longer part of the
code checks, but can be re-added if requested. The reason to drop was
that it does not play nicely with pre-commit, and lots of its
functionality and responsibilities are actually covered in ruff.
* Add dev extra to pyproject.toml for development installs
* Clarify that pre-commit contains only Python and Bazel hooks
* Add one-line docstrings to Bazel modules
* Apply buildifier pre-commit fixes to Bazel files
* Apply pre-commit fixes to Python files
* Supply --profile=black to isort to prevent conflicts
* Fix nanobind build file formatting
* Add tooling configs to `pyproject.toml`
In particular, set line length 80 for all Python files.
* Reformat all Python files to line length 80, fix return type annotations
Also ignores the `tools/compare.py` and `tools/gbench/report.py` files
for mypy, since they emit a barrage of errors which we can deal with
later. The errors are mostly related to dynamic classmethod definition.
