Add trimming tests for System.ComponentModel.TypeConverter changes

[layomia]

Contributes to #37677 (Strip the ILLinkTrim.xml file from the System.ComponentModel.TypeConverter assembly - #37402)

[ghost]

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[layomia]

I'm not the best way to test the change in https://github.com/dotnet/runtime/pull/37402/files#diff-64cb2690a89a375e7a29b0c7d3651ba5R704.

[eerhardt]

I'm not the best way to test the change in https://github.com/dotnet/runtime/pull/37402/files#diff-64cb2690a89a375e7a29b0c7d3651ba5R704.

These would be tests for the following:

runtime/src/libraries/System.ComponentModel.TypeConverter/src/ILLinkTrim_LibraryBuild.xml

Lines 9 to 12 in a8d8b4a

	<!-- The following types support the CLR's IClassFactory2 marshaling from CoreLib: -->
	<type fullname="System.ComponentModel.LicenseManager/LicenseInteropHelper" />
	<type fullname="System.ComponentModel.LicenseManager/CLRLicenseContext" />
	<type fullname="System.ComponentModel.LicenseManager/LicInfoHelperLicenseContext" />

I don't know how to test this without writing C/C++ code. Maybe @vitek-karas or @elinor-fung would know?

---

Also, it might make sense to ensure that the TypeDescriptionProvider attributes on XElement and XAttribute work correctly.
You can test this by calling TypeDescriptor.GetProvider passing in typeof(XElement).

[elinor-fung]

I don't know how to test this without writing C/C++ code.

I think those types are only used during COM activation - activating either a native or managed COM server should exercise them. The problem with a managed COM server is that I'm not sure how building one fits within the testing infrastructure, since we don't/can't use framework references like a normal build considering they are the things under test. Usually, building a managed COM server would make use of the native comhost.dll that is part of the Microsoft.NETCore.App.Host package - it could be mimicked by copying/renaming comhost.dll and creating a .json file. (The coreclr COM tests use their own custom native shim instead.) The other thing I see with using a managed COM server is that I don't think some of the types used for activation (e.g. ComActivator) are marked to be kept (at least that I could see)? What is the expectation for trimmed apps loading COM / components in general?

[eerhardt]

LGTM

[layomia]

@elinor-fung thanks for the reply. I've logged an issue to address the tests - #38417.