black: use multiline exclude definition
Our excludes list is pretty complicated, so let's give ourselves some
readability. Black treats multiline exclude definitions as verbse
regular expressions, so we can split this up and make it easier to
consume.
Differential Revision: https://phab.mercurial-scm.org/D7089
[tool.black]
line-length = 80
exclude = '''
build/
| wheelhouse/
| dist/
| packages/
| \.hg/
| \.mypy_cache/
| \.venv/
| mercurial/thirdparty/
| hgext/fsmonitor/pywatchman/
| contrib/python-zstandard/
'''
skip-string-normalization = true
quiet = true