test_runner: replace yapf with black and isort

setup.cfg

@@ -1,43 +0,0 @@
-# Just trying to gather linter settings in one file.
-# I wonder if there's a way to de-duplicate them...
-
-[flake8]
-max-line-length = 100
-
-[pycodestyle]
-max-line-length = 100
-
-[yapf]
-based_on_style = pep8
-column_limit = 100
-split_all_top_level_comma_separated_values = true
-
-[mypy]
-# mypy uses regex
-exclude = ^vendor/
-# some tests don't typecheck when this flag is set
-check_untyped_defs = false
-
-# Help mypy find imports when running against list of individual files.
-# Without this line it would behave differently when executed on the entire project.
-mypy_path = $MYPY_CONFIG_FILE_DIR:$MYPY_CONFIG_FILE_DIR/test_runner
-
-disallow_incomplete_defs = false
-disallow_untyped_calls = false
-disallow_untyped_decorators = false
-disallow_untyped_defs = false
-strict = true
-
-[mypy-asyncpg.*]
-# There is some work in progress, though: https://github.com/MagicStack/asyncpg/pull/577
-ignore_missing_imports = true
-
-[mypy-pg8000.*]
-# Used only in testing clients
-ignore_missing_imports = true
-
-[mypy-cached_property.*]
-ignore_missing_imports = true
-
-[mypy-pytest.*]
-ignore_missing_imports = true