Support navigation when having nested test fixtures

[Sam13]

Assume you have a class Foo and a corresponding test fixture. In the test fixture you have nested fixtures for different test scenarios. For example:

internal sealed class FooTest
{
    [TestFixture]
    internal sealed class FooInScenario1
    {
        ...
    }

    [TestFixture]
    internal sealed class FooInScenario2
    {
        ...
    }
}

Navigation does not work when trying to navigate from nested test fixture back to class under test. Instead a question appears whether a new production class should be generated...

Using test linker 1.4.2 and R# 2017.1.3