Provide a setting to always show the selected interpreter

[brettcannon]

As of now the selected interpreter is hidden when you are not viewing Python files or special Python-specific files. But some folks want the interpreter info to show more often, e.g. extensions supporting DSLs requiring Python, Django devs editing their HTML file templates, etc.

So we want to provide a setting (name TBD) that will let folks opt into having the selected interpreter to always be displayed when the Python extension is loaded.

[wouterdb]

@brettcannon is there a way we can make this move forward?

[brettcannon]

@wouterdb unfortunately the hold up is entirely on me and @luabud to make a decision about the language status menu and whether/how we want to use it. Once that's decided on then that will inform whether this setting is even necessary. We are planning to make the decision this week or next.

[karrtikr]

Related: #18930

[brettcannon]

We've decided to implement this, so votes are not required to make it into our queue, but further votes will help us prioritize getting to it. 🙂

[karrtikr]

Verification steps:

This affects the interpreter information in status bar:

• Install the pre-release version of the extension:
  
• Setting name: python.interpreter.infoVisibility.
• Verify setting is only available at User/Machine level.
• Verify the description of the setting and each value aligns with the behavior.
• When set to onPythonRelated, verify information in status bar disappears if non-Python files are in focus (settings.json is considered a Python related file).
• Verify we don't need to reload for setting change to take effect.