Tweak Python 3 setup

[brettcannon]

• Drop an unnecessary * at the end of a file name for copying
• Don't have pip bother checking for a newer version of pip (assume it's new enough as it came with the latest version of Python which the container is pulling from)
• Don't cache wheel files (to keep the image smaller)
• Specify the location of the pylint executable to turn on Pylint development

[Chuxel]

One comment inline, but otherwise looks awesome! Thanks so much for doing it.

BTW - I gave the Python tools team write access to the repo to make merging in changes easier if Christof and I are both tied up for some reason.

[brettcannon]

@Chuxel which Python tools team did you give access? It's a bit nebulous as we have several teams on GitHub across us and various companion teams. 😁

[Chuxel]

@brettcannon I gave pvsc-team write access - LMK if I should use a different one.

[Chuxel]

Tested it out - LGTM!