Update Environments section in Python language doc

[karrtikr]

https://code.visualstudio.com/docs/languages/python#_environments

• Update screenshot to not use Anaconda, and show interpreters on right hand side instead
• Update the Invalid interpreter status bar item
• Correct debugging line here:

  The selected environment is used for IntelliSense, auto-completions, linting, formatting, and any other language-related feature other than debugging.
  

• Maybe teach how to open command palette instead of screenshot?
• Take section out on installing packages