Yes, this is completely unimportant. Don't ask me why I bothered, I'm
not really sure.

I was using pytest.__file__ as a directory, but in 5.3.2, pytest changed
to be a package, so that wasn't the site-packages directory anymore, and
our .pth file was written someplace useless.

Now we don't rely on the structure of pytest (why did we ever?), and it
works again.

python3 -m pip install codespell

codespell --ignore-words-list="ba,cant,datas,hart,linke,ned,nin,overthere,upto" --skip="*.js"

* Fix typos discovered by codespell

* datas

* intgers ==> integers

Now when a goldtest has a failure, the actual mismatched output will be written
to the tests/actual directory.

Along the way, I removed some obsolete settings which were only used by unittest
and unittest_mixins, which we no longer use:

- COVERAGE_KEEP_TMP
- COVERAGE_ENV_ID
- $TMPDIR/coverage_test

Before this commit, the GetZipBytesTest.test_get_encoded_zip_files test
was flaky on Python 3.10.0a7.  Since I had just added new files to the
common zip file, I tried splitting the newly added stuff into its own
file, and that seemed to fix the problem.

People don't use .egg much anymore, distutils is showing deprecation
warnings, and coverage.py only deals with them the same way it deals
with .zip files, so let's just rely on a .zip test to cover that.