Update the Index and Range interfaces and tests

[tarekgh]

No description provided.

[tarekgh]

This depends on dotnet/coreclr#24036

[tarekgh]

CC @stephentoub @agocke @terrajobst @GrabYourPitchforks @joshfree @jkotas

[GrabYourPitchforks]

Utf8String changes LGTM. Thanks!

[terrajobst]

Why is this marked NO MERGE? PResumably because we want to wait for dotnet/coreclr#24036 but this is just excluding APIs, so why would it matter?

[tarekgh]

Why is this marked NO MERGE? PResumably because we want to wait for dotnet/coreclr#24036 but this is just excluding APIs, so why would it matter?

I am expecting the api compat checks will fail before getting the updated bits from coreclr. I am not expecting a compilation/runtime failure though. let's wait for the CI to see if this is the case or we can just merge it if it comes green.

[tarekgh]

@terrajobst I confirmed the api compat failed because we have added the Slice method to Utf8String. I can fix that in this PR but this will cause it to break again when getting the updated coreclr bits.

[tarekgh]

linking to the compiler fix dotnet/roslyn#35004 which will make the following test to compile and work fine

Assert.Throws<ArgumentOutOfRangeException>(() => new Span<char>(s.ToCharArray())[range])

[terrajobst]

let's wait for the CI to see if this is the case or we can just merge it if it comes green.

Makes sense. I'll wait untilt he CoreFX change is in so that I can update .NET Standard accordingly.

[stephentoub]

Nice. Thanks.

[tarekgh]

Closing this one as the commits included here are picked up in the PR #36976