Bug 1654103: Standardize on Black for Python code in `mozilla-central`. r=remote-protocol-reviewers,marionette-reviewers,webdriver-reviewers,perftest-reviewers,devtools-backward-compat-reviewers,jgilbert,preferences-reviewers,sylvestre,maja_zf,webcompat-reviewers,denschub,ntim,whimboo,sparky Allow-list all Python code in tree for use with the black linter, and re-format all code in-tree accordingly. To produce this patch I did all of the following: 1. Make changes to tools/lint/black.yml to remove include: stanza and update list of source extensions. 2. Run ./mach lint --linter black --fix 3. Make some ad-hoc manual updates to python/mozbuild/mozbuild/test/configure/test_configure.py -- it has some hard-coded line numbers that the reformat breaks. 4. Make some ad-hoc manual updates to `testing/marionette/client/setup.py`, `testing/marionette/harness/setup.py`, and `testing/firefox-ui/harness/setup.py`, which have hard-coded regexes that break after the reformat. 5. Add a set of exclusions to black.yml. These will be deleted in a follow-up bug (1672023). # ignore-this-changeset Differential Revision: https://phabricator.services.mozilla.com/D94045