Re-land the sonic decl/impl split with fallback discovery parse reuse by chsienki · Pull Request #84844 · dotnet/roslyn

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Re-land the sonic decl/impl split with fallback discovery parse reuse - #84844

Re-land the sonic decl/impl split with fallback discovery parse reuse#84844
chsienki merged 8 commits into
dotnet:mainfrom
chsienki:un-revert/sonic-fix