Generic classes with differently typed [Arguments] rows produce different test sets in source-gen and reflection modes #7118

Summary

On a generic test class whose [Arguments] rows infer different type arguments, the two modes produce different test sets.

Repro

[Arguments(1)]
[Arguments("a")]
public class MixedRows<T>(T value)
{
    [Test]
    [Arguments(1)]
    [Arguments("a")]
    public void Test<TMethod>(TMethod arg) { }
}

• Source-gen mode: every method row runs in every class instantiation, so mistyped combinations such as Test<int>("a") are produced. That gives 4 tests, 1 of which fails on argument conversion.
• Reflection mode: each row runs only in the instantiation its own types infer. That gives 2 tests, both passing.

Reflection mode's behaviour looks like the intended one, so source-gen should probably stop pairing rows with instantiations whose types they do not match.

Notes

Found while addressing review on #7094; the exact repro shape should be confirmed when picked up. Related: #7106, #7111.