Plumb source generators through ref-packs

[ericstj]

Implement https://github.com/dotnet/designs/blob/main/accepted/2021/InboxSourceGenerators.md

• Add support in SDK for raising analyzer items from the ref-pack, and conflict-resolve them. Add support for analyzers from ref-packs sdk#18501 (Support conflict resolution for @(Analyzer)s sdk#16772)
• Add support to the shared framework SDK to understand analyzers and write appropriate entries to frameworklist. Recognize files in ref-pack under "analyzers" as analyzers and write them to the frameworkList arcade#7561
• Plug dotnet/runtime source-generators into ref pack and asp.net transport package. Add analyzers to ref-pack / ASP.NET transport package #54950
• Add support to ASPNetCore and ingest transport package Add support for packaging analyzers into ref-pack aspnetcore#33977

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Issue Details

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Implement https://github.com/dotnet/designs/blob/main/accepted/2021/InboxSourceGenerators.md

• Add support in SDK for raising analyzer items from the ref-pack, and conflict-resolve them. Add support for analyzers from ref-packs sdk#18501
• Add support to the shared framework SDK to understand analyzers and write appropriate entries to frameworklist. Recognize files in ref-pack under "analyzers" as analyzers and write them to the frameworkList arcade#7561
• Plug dotnet/runtime source-generators into ref pack and asp.net transport package. Need to be able to include Analyzers / Source generators in refpack / transport packages  #50621

Author:	ericstj
Assignees:	ericstj
Labels:	area-Infrastructure-libraries, untriaged
Milestone:	-