Add some integration tests for new [DoesNotReturn] feat

[MarcoRossignoli]

@kevin-montrose did a great job on it #904 and added also some tests

https://github.com/coverlet-coverage/coverlet/blob/master/test/coverlet.core.tests/Instrumentation/InstrumenterTests.cs#L647
https://github.com/coverlet-coverage/coverlet/blob/master/test/coverlet.core.tests/Samples/Instrumentation.DoesNotReturn.cs

We should add also some integration tests with same sample to cover also parameter option passed in(i.e. /p:DoesNotReturnAttribute="DoesNotReturnAttribute,OtherAttribute"):

1. Add a file https://github.com/coverlet-coverage/coverlet/tree/master/test/coverlet.core.tests/Coverage called CoverageTests.DoesNotReturn.cs
2. Add one test for every samples in file https://github.com/coverlet-coverage/coverlet/blob/master/test/coverlet.core.tests/Samples/Instrumentation.DoesNotReturn.cs

[daveMueller]

I would work on this but I got a questions on how this works. Currently in the test (https://github.com/coverlet-coverage/coverlet/blob/master/test/coverlet.core.tests/Instrumentation/InstrumenterTests.cs#L647) the notReachableLines are not instrumented even when there is no DoesNotReturnAttributes.
What ever DoesNotReturnAttributes parameter I pass to the constructor the test always succeeds.

coverlet/test/coverlet.core.tests/Instrumentation/InstrumenterTests.cs

Lines 246 to 247 in dd2237a

	Instrumenter instrumenter = new Instrumenter(module, identifier, Array.Empty<string>(), Array.Empty<string>(), Array.Empty<string>(), attributesToIgnore, Array.Empty<string>(), false, false,
	_mockLogger.Object, instrumentationHelper, new FileSystem(), new SourceRootTranslator(_mockLogger.Object, new FileSystem()), new CecilSymbolHelper());

In my humble understanding the notReachableLines should only be excluded from instrumentation when the parameter is set? Or not?

[MarcoRossignoli]

By defauilt DoesNotReturnAttribute is always added https://github.com/coverlet-coverage/coverlet/blob/master/src/coverlet.core/Instrumentation/Instrumenter.cs#L83

New feat allows also to add new users defined attributes

[daveMueller]

Ahh ok thanks. I didn't check what happens in PrepareAttributes(...) 🙈. You can assign this to me then.

[MarcoRossignoli]

No worries, thanks!(I know I have your PR in queue)

[daveMueller]

@MarcoRossignoli Could you take a peek at https://github.com/daveMueller/coverlet/blob/946_Integration_Tests/test/coverlet.core.tests/Coverage/CoverageTests.DoesNotReturn.cs.
Is this what you intended? When using the samples in Instrumentation.DoesNotReturn.cs it doesn't really make sense to pass a doesNotReturnAttribute to the instrumenter because it defaults to DoesNotReturnAttribute.

[MarcoRossignoli]

When using the samples in Instrumentation.DoesNotReturn.cs it doesn't really make sense to pass a doesNotReturnAttribute to the instrumenter because it defaults to DoesNotReturnAttribute.

Yep we can for now avoid to add the attributes overload to test helper class, we use build-in DoesNotReturnAttribute