mypy: Exclude only 20 files that are still failing (#5608)

* DRAFT: Run a mypy reality check

Let's see what is required to finish  #4052

* mypy --ignore-missing-imports --install-types --non-interactive

* Check our progress...

* Update build.yml

* Update build.yml

* Update build.yml

* Update build.yml

* mypy --exclude 20 files

* --exclude with no `=`

* Update build.yml

* 558 character regex!!!

* With quotes

* mypy.ini: mega exclude

* Update mypy.ini

* Update build.yml

* Update mypy.ini

* Update build.yml

* Update mypy.ini

* .py --> .p*

* Escape the dots!: `.` --> `\.`

* Remove the comment

* Leading slash

* Update mypy.ini

Co-authored-by: Dylan Buchi <[email protected]>

Co-authored-by: Dylan Buchi <[email protected]>