Resumable Code RFC sample code is missing

[majocha]

At some point the sample code that resided in benchmarks/TaskPerf went missing.
https://github.com/dotnet/fsharp/tree/f45ef819b5310de521645dbc68ccbfc57f8edda4/tests/benchmarks/TaskPerf

In effect, all the links to it in Resumable Code RFC are broken.

[T-Gro]

Thanks for spotting this.
It would be better if the RFC pointed to snapshots (from F# 6 time of the repo).

[brianrourkeboll]

I think they were removed in #16812. Should we update the RFC to use permalinks?