Change prefix for _importlib_modulespec names

[pkch]

(Not ready for merging)

This PR is meaningless without python/mypy#3107; if that one is approved, this would fix the type reported for modules from _importlib_modulespec.ModuleType to types.ModuleType. (There is no dependency in the other direction.)

This PR is related to python/mypy#3106.

[pkch]

Next commit would break mypy unless python/mypy#3107 is merged.

Note: I wasn't sure about this line in 2/abc.pyi:

types = ...  # type: module

which I changed to

types = ...  # type: ModuleType

I'm afraid I might be breaking something even though the tests pass.

Also, werkzeug stubs had:

class module(ModuleType):
  def __getattr__(self, name): ...
  def __dir__(self): ...

I removed them, but I also suspect they may serve some non-obvious purpose.

[JelleZijlstra]

This probably shouldn't be here at all. (I'm guessing tokenize just imports re.)

[JelleZijlstra]

If we go down this route, we should prefix it with _ to make clear that this name isn't actually part of this module. However, I'd prefer to just hardcode the location of ModuleType in mypy and not add special handling in typeshed.

[pkch]

I don't have an opinion on this, I would be happy to hard code it in mypy. Just wasn't sure if it's ok given that it's hard to find later when more circular import definitions happen.

[pkch]

I replaced the MYPY_MODULE with hard-coded remapping; so this PR simply replaces module with types.ModuleType. It is blocked by python/mypy#3107, but does not block it.

[pkch]

Superceded by #1156