Add params ReadOnlySpan<T> overloads

[Jozkee]

Fixes #77873

[dotnet-issue-labeler]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

[Jozkee]

I'm really scratching my head trying to understand why some projects fail to build. That's also why I sent this as draft.
cc @dotnet/area-infrastructure-libraries

Unix:
CSC : error CS0656: Missing compiler required member 'System.Runtime.InteropServices.MemoryMarshal.CreateReadOnlySpan' [/__w/1/s/src/libraries/System.IO.Pipes.AccessControl/src/System.IO.Pipes.AccessControl.csproj::TargetFramework=net9.0]
CSC : error CS0656: Missing compiler required member 'System.Runtime.InteropServices.MemoryMarshal.CreateReadOnlySpan' [/__w/1/s/src/libraries/System.Threading.Tasks.Dataflow/src/System.Threading.Tasks.Dataflow.csproj::TargetFramework=net9.0]
CSC : error CS0656: Missing compiler required member 'System.Runtime.InteropServices.MemoryMarshal.CreateReadOnlySpan' [/__w/1/s/src/libraries/System.Threading.Channels/src/System.Threading.Channels.csproj::TargetFramework=net9.0]
CSC : error CS0656: Missing compiler required member 'System.Runtime.InteropServices.MemoryMarshal.CreateReadOnlySpan' [/__w/1/s/src/libraries/System.IO.FileSystem.AccessControl/src/System.IO.FileSystem.AccessControl.csproj::TargetFramework=net9.0]
CSC : error CS0656: Missing compiler required member 'System.Runtime.InteropServices.MemoryMarshal.CreateReadOnlySpan' [/__w/1/s/src/libraries/System.Collections.NonGeneric/src/System.Collections.NonGeneric.csproj]
CSC : error CS0656: Missing compiler required member 'System.Runtime.InteropServices.MemoryMarshal.CreateReadOnlySpan' [/__w/1/s/src/libraries/System.Net.Http.Json/src/System.Net.Http.Json.csproj::TargetFramework=net9.0]

Windows:
CSC : error CS0656: Missing compiler required member 'System.Runtime.InteropServices.MemoryMarshal.CreateReadOnlySpan' [D:\a\_work\1\s\src\libraries\System.IO.IsolatedStorage\src\System.IO.IsolatedStorage.csproj::TargetFramework=net9.0-windows]

[stephentoub]

@Jozkee, try adding <Reference Include="System.Memory" /> to the .csproj.

That said, I'm not sure why CreateReadOnlySpan would be a required member, since I'd have expected there to be fallback strategies if it's not available (that said, I'm glad this error'd for us, as otherwise presumably we would have been silently falling back to slower support). @AlekseyTs?

[Jozkee]

FWIW: I brute-forced it and noticed the error goes away if I exclude the new string.Join overloads. @stephentoub Adding a reference to System.Memory fixes it too, is that the path we want to follow?

[stephentoub]

Adding a reference to System.Memory fixes it too, is that the path we want to follow?

Yes

[AlekseyTs]

@Jozkee, try adding <Reference Include="System.Memory" /> to the .csproj.

That said, I'm not sure why CreateReadOnlySpan would be a required member, since I'd have expected there to be fallback strategies if it's not available (that said, I'm glad this error'd for us, as otherwise presumably we would have been silently falling back to slower support). @AlekseyTs?

I assume a ReadOnlySpan overload is getting chosen. What is needed to create one is actually defined by "Collection Expressions" feature. CC @cston.