Support "not contains" operator on TestCaseFilter CLI parameter

[julealgon]

I'd like to propose the introduction of a "not contains" (!~) operator in vstest.console TestCaseFilter.

For vstest.console, we currently have the following operations:

• equals (=)
• not equals (!=)
• contains (~)

This is bad because it allows you to negate equality but not the contains, it is not orthogonal.

Supporting "not contains" would allow some business cases that are completely impossible today, like:

Run all tests that are not in namespace X

I needed this behavior recently but it is completely impossible to represent it using the current operators. I'll be forced to split the tests in 2 different projects or call vstest.console twice to make it work, and this seems unnecessary to me.

I feel like a generic "not" operator (!) that could negate any expression would be more flexible, but that is a bit more work and would probably also impact the != functionality. This is why I'm limiting my suggestion to a less flexible, "hardcoded" not contains !~.