WIP: Adding a new DataAttribute to improve specifying realsig, optimize and baselines.

[KevinRansom]

Todo:
-[] Convert more tests to use the new attribute.

[github-actions]

✅ No release notes required

[T-Gro]

Would it be possible to use https://learn.microsoft.com/en-us/dotnet/fsharp/language-reference/caller-information instead?
Why exactly do we need it?

[KevinRansom]

@T-Gro , no. The Xunit.Sdk.DataAttribute.GetData override requires a MethodInfo instance. The caller-information attributes return the names of the member, the source file and line numbers.

Here is the Xunit description:
https://csharp-tokyo.github.io/xUnit-Hands-on/class_xunit_1_1_sdk_1_1_data_attribute.html#ab74ea9efe0a313e19ac0e8d8136a9071

[KevinRansom]

We need it, because GetData _ = is how XUnit retrieves the test data instance, and in this case we are using the DirectoryAttribute to create a compiler instance, and so we need to 'pretend' we are being xunit. It is true that our DirectoryAttribute doesn't actually use it, but we do need an instance to even invoke the method. And there is a decent probablility that at some point in the future DirectoryAttribute.GetData() will use it, so I didn't want to pass Unchecked.DefaultOf.

[majocha]

If we reuse the functionality of DirectoryAttribute possibly we could extract createCompilationUnit from it into a module or maybe inherit?

[KevinRansom]

@majocha --- I'm still trying to figure out what we need. But we can certainly refactor, if necessary once we understand the necessities.