python-packages: Add usr/bin symlinks without "3" suffix

python-packages: Add usr/bin symlinks without "3" suffix

Previously, binaries installed by Python packages will have a
non-suffixed Python 2 version and a suffixed Python 3 version, e.g. pip
and pip3. With the removal of Python 2, the non-suffixed names are no
longer taken.

This adds symlinks for the non-suffixed names linking to the suffixed
scripts (or in the case of pip, easy_install, and python-config, to the
fully-versioned scripts).

Signed-off-by: Jeffery To <redacted>