ci: bump pytype to 2022.03.29 This is as far as we can go without running into issues with the vendored `attr` package. I tried updating that to the latest, and not only did it not fix the issue, but test-util.py failed due to some poking at `attr` internals that apparently is no longer valid. The `libcst` package is now pinned to what I have locally because trying to install the latest (0.4.7) complains that it can't find the Rust compiler. We should probably use a requirements file instead (and/or figure out why it can't find the Rust compiler), but I don't feel like dealing with another side quest.

typing: suppress a few attribute errors in url.py These are newly detected by pytype 2022.03.21. Not sure what is going on here- `realhostport` and `headers` are added outside of the constructor, so that makes sense. But PyCharm also thinks the private methods don't exist, though when clicking through the class hierarchy, it shows in the py3.9 source code.