Enable embedding *.res resources via ilasm

[jkoritzinsky]

As mentioned in dotnet/coreclr#20818, ilasm delegates out a step of the resource-embedding process to a process named CvtRes.exe. We don't ship CvtRes.exe with .NET Core (it's also not OSS). So, we need to come up with a plan that allows us to enable resource embedding of *.res files with ilasm on .NET Core.

[TIHan]

Are there any customers blocked by this issue?

[jkoritzinsky]

We have some tests that we can't enable while this issue is present since the lack of this feature means that App Manifests are dropped in the ilasm-ildasm round-trip tests. There are no customers that have asked for this feature specifically though.

[jkoritzinsky]

Actually, looking at the issue reference logs above, #48046 is a customer request for this feature (it's just about the ilasm flag, not the underlying feature). One of these can be closed as a duplicate of the other.

[TIHan]

Not sure how quickly we could add support for this, I imagine it would take some time and the only immediate gain would be enabling some of those round-trip tests.

[jkoritzinsky]

Roslyn already has a managed port of CvtRes, so we could port their OSS port back to C++. Or I could eventually have time to finish my managed port of ILAsm and we could use the Roslyn version as-is.