Make Testing more approachable

[isidorn]

Based on our brainstorm here are some action items we could do:
-[ ] Show testing viewlet even if there is no testing extension installed (and the user has opened a folder in VS Code) @connor4312
* The testing viewlet without a test extension should show the welcome view. And have a "blue button" to take users to the Extensions view with category:testing. Optional: have smart detection to identify what test extension is best suited for the workspace.

• Recommend test extensions using current notification when a specific test config file is open @isidorn
• Check with Python team if the testing setup can be more automatic, and that it does not require a manual configure @isidorn
• Revisit the testing docs, and make sure all the latest features are covered @ntrogh

I am opportunistically assigning this to May.

[isidorn]

Ok, marking the last two items as done. I discussed for Python test discovery with @luabud and here's what she says

"We don't know which framework the tests should be configured with, and there may be a lot of different configs and arguments that people need to pass so tests can successfully be discovered. If we tried to something automatically without requiring user config, most likely we would show a failure on the test view.
pytest needs to be installed in user's environment for it to perform discovery. When people configure their tests to use pytest and it's not installed, we automatically install it on their behalf. We ofc can't do that automatically on load though, so we'd need to figure out a way to handle that part."

For the remaining two items, I will move this issue to July. @connor4312 do you have any concerns about showing extension recommendation on test config file open?

@connor4312 What are your thoughts on showing the testing viewlet on by default with welcome view for Workspaces with a folder?