Reuse libraries in pip own's _vendor

[oz123]

There are some libraries that we vendor, and are already found in pip/_vendor. These are;

colorma
tomli
urllib3
pyparsing
packaging
pep517
platformdirs
idna
distlib
six

Removing them from our own vendor is going to serve pipenv users with a smaller package and remove duplication.
It is also worth noting that most of these libraries are probably not going to be removed from pip since they are crucial for
parsing of dependencies.

Those who are not really related like tomli, colorama and urllib3 are crucial for other reasons and I also don't see them
being removed from pip anytime soon.

[matteius]

@oz123 Anything left on this one?

[oz123]

These are still major tasks.
attrs is still an open issue. It's a large one though.
colorama is still open issue.
pyparsing.

Some other smaller libs are too ...