Add granular suppressions for linker warnings

[layomia]

Addresses #38033.

cc @mateoatr

[ghost]

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[ViktorHofer]

In the past we put the rd.xml files into the Properties (AppDesigner) folder where other configuration files might live as well. Is there a reason for the extra ILLink folder?

[eerhardt]

Is there a reason for the extra ILLink folder?

There are a set of ILLink related files that traditionally have been in the root of the project. Mono started grouping them into a folder specifically for this area, and it has worked out well as we've been adding more files in this space. We are already putting ILLink related files in src/ILLink folders. This change is just making all libraries uniform.

In the worst case, we have almost 10 ILLinker files for one library - https://github.com/dotnet/runtime/tree/master/src/libraries/System.Private.CoreLib/src/ILLink

[eerhardt]

Assuming the CI is green, this LGTM. Thanks for pulling this off - great work.

[ViktorHofer]

There are a set of ILLink related files that traditionally have been in the root of the project.

Right I agree that we shouldn't have them in the project root. I was asking if it would make more sense to put them into the Properties folder which is used for other config files as well?

[eerhardt]

I was asking if it would make more sense to put them into the Properties folder which is used for other config files as well?

The only existing places I see using a Properties folder is for InternalsVisibleTo.cs files.

This PR is just following the established pattern and making the repo consistent. If you feel strongly the existing pattern should be changed, can you log an issue for it?