Deliver SignalR Dependencies

[KrzysztofCwalina]

SignalR just released an alpha using several components from corefxlab. We need to productize these components:

• System.Binary Issue: Add Span<T> Binary Reader/Writer APIs #23601 PR: Add Span<T> Binary Reader/Writer APIs corefx#24400
• System.Binary.Base64 Issue: dotnet/corefx#24568
• System.Text.Primitives Issue: dotnet/corefx#24607
• System.Threading.Tasks.Channels Issue: dotnet/corefx#24823
• System.IO.Pipelines Issue: dotnet/corefx#24824
• System.Text.Encodings.Web.Utf8 Issue: dotnet/corefx#24825
• System.IO.Compression.Brotli Issue: dotnet/corefx#24826
• System.Collections.Sequences Issue: dotnet/corefx#25105
• System.Text.Formatting Issue: dotnet/corefx#25249 Edit: Not needed by SignalR

[joshfree]

@dotnet/corefxlab-contrib please treat this as the uber bug tracking the work necessary for the SignalR preview releases. Please keep this bug up to date and reference it with your PRs

[muratg]

👀

[tarekgh]

@KrzysztofCwalina @joshfree do we still have more to do here? or we can close this one?