Gather appropriate list of managed runtime assemblies for crossen and (eventually) linker

[nguerrera]

Today, crossgen (new ReadyToRun feature) operates over all files to publish and filters out what is not IL. We have decided that the compilation set should be restricted by default to the set of files that we deem are runtime managed assets and designate as such in the .deps.json.

As of now, there isn't an exact match for this list that is readily available. _ResolvedCopyLocalPublishAssets + IntermediateAssembly is close.

I suspect that with #3080, this will be easier to do, but I didn't review in detail yet.

[nguerrera]

cc @sbomer @fadimounir @dsplaisted

[fadimounir]

@nguerrera Can we mark this issue as blocking to R2R/ILLinker scenarios to bump the priority?

[dagood]

Based on the milestone change of 3.0.1xx => 3.1.1xx, I'm moving a backing issue in Core-Setup to 3.1 as well: https://github.com/dotnet/core-setup/issues/7728. Let me know if there's a reason to get https://github.com/dotnet/core-setup/issues/7728 done for 3.0 rather than 3.1 in case I misunderstood.