Generated Protobuf library code is not compatible with typeshed's protobuf type stubs

[thundergolfer]

Not too confident this will be easily fixed on the typeshed side -> python/typeshed#2521

[thundergolfer]

✝️ 👨🏾‍⚕️

I think I've got a 'bandaid' solution. Add the following to the mypy.ini:

[mypy-google.protobuf.*]
follow_imports_for_stubs = True
follow_imports = skip

making sure that that config is placed above any more general config like what's shown below.

[mypy-google.*]
ignore_missing_imports = True

The effect is that the (incorrect) protobuf typeshed stubs aren't looked at, and thus the errors within don't break our builds. The relevant piece of the MyPy docs are:

Used in conjunction with follow_imports=skip, this can be used to suppress the import of a module from typeshed, replacing it with Any.