Restrict ConditionalMemberKinds to reflect what ConditionalTestDiscoverer reflects on

[MichalStrehovsky]

Matching code is this:

arcade/src/Microsoft.DotNet.XUnitExtensions.Shared/Discoverers/ConditionalTestDiscoverer.cs

Lines 170 to 190 in 302c350

	internal static Func<bool> LookupConditionalMember(Type t, string name)
	{
	if (t == null || name == null)
	return null;
	TypeInfo ti = t.GetTypeInfo();
	MethodInfo mi = ti.GetDeclaredMethod(name);
	if (mi != null && mi.IsStatic && mi.GetParameters().Length == 0 && mi.ReturnType == typeof(bool))
	return () => (bool)mi.Invoke(null, null);
	PropertyInfo pi = ti.GetDeclaredProperty(name);
	if (pi != null && pi.PropertyType == typeof(bool) && pi.GetMethod != null && pi.GetMethod.IsStatic && pi.GetMethod.GetParameters().Length == 0)
	return () => (bool)pi.GetValue(null);
	FieldInfo fi = ti.GetDeclaredField(name);
	if (fi != null && fi.FieldType == typeof(bool) && fi.IsStatic)
	return () => (bool)fi.GetValue(null);
	return LookupConditionalMember(ti.BaseType, name);
	}

It doesn't flow through because xUnit abstracts away reflection.

The capture is unnecessarily broad and causes spurious warnings in dotnet/runtime repo.

Cc @dotnet/illink

[sbomer]

LGTM, thanks!