Vendoring wheels has three benefits:
* There's far less files, so Firefox checkouts will be smaller.
* It works around `zipp` not allowing `pip install`
from extracted source `tar.gz` files. Now, we should
be able to use the pip resolver against vendored
packages, which will be needed for future
mach virtualenv work.
* `./mach vendor python` takes far less time to execute.
Since we need the raw Python to be available to add to the `sys.path`,
we extract the wheels before putting them in tree.
Due to the structure of some wheels being less nested
than of a source `tar.gz`, `common_virtualenv_packages`
needed to be adjusted accordingly.
`install_pip_package()` had to be tweaked as well since you can't
`pip install` an extracted wheel. So, we "re-bundle" the wheel
before installing from a vendored package.
Replace python packages with wheels where possible
This contains the vendoring changes caused by the
last patch.
For reviewing, there's a couple things to note:
* A bunch of files are deleted, since there's generally
less files in a wheel than in a source archive.
* There's a new `.dist-info` directory for each
extracted wheel, so expect roughly 5 or
6 new files for each wheel'd package.
* There should be no source code changes other than
moves from package names changing from having
`-` to having `_`.
Differential Revision: https://phabricator.services.mozilla.com/D116512
Mike Hommey