typing: add more type hints to the errors module
These were found by looking for `Any` types in the generated `*.pyi` file after
running the tests. There are some more complicated types that I'm not sure of,
and am leaving untyped. I also can't figure out how to get `self.hint` to be
anything other than `Any` in most classes.
Differential Revision: https://phab.mercurial-scm.org/D11719
[build-system]
requires = ["setuptools", "wheel"]
[tool.black]
line-length = 80
exclude = '''
build/
| wheelhouse/
| dist/
| packages/
| \.hg/
| \.mypy_cache/
| \.venv/
| mercurial/thirdparty/
'''
skip-string-normalization = true
quiet = true