Add DoesNotReturnIf to Assert.IsTrue/Assert.IsFalse and DoesNotReturn to Assert.Fail

[dferretti]

Fixes #1004

When adding these attributes, I did hesitate on the IsTrue/IsFalse overloads accepting nullable bools, because it does look odd to see
[DoesNotReturnIf(true)] bool? condition
right next to a check like
if (condition == true || condition == null)
knowing that for both true and null the method will not return - but only for true will the nullability analysis kick in. Passing null will result in the call site still not knowing if the method returns or not so the user will still have to perform their own additional check.

But my thought process was that the attribute is still accurate and still helps. [DoesNotReturnIf(true)] means just that - the method does not return if the parameter exactly matches true. It does not say whether or not the method returns if false or null are passed in.
Even though in this case we know that IsFalse(null) will not return, there is not a way to represent that with the current DoesNotReturnIf attribute.

[ghost]

All CLA requirements met.

[dferretti]

cc @Haplois

[Haplois]

Thank you for the contribution @dferretti, merging!