Perf Test Coverage: Port Xamarin benchmarks to xunit

[valenis]

Port relevant benchmarks from:
https://github.com/xamarin/benchmarker/tree/master/tests to xunit and enable them for coreclr

category:cq
theme:benchmarks
skill-level:beginner
cost:medium

[am11]

Do we still need this? given:

• we have https://github.com/dotnet/performance repo for various scenarios/benchmarks.
• https://github.com/xamarin/benchmarker is deprecated.

cc @jkotas, @EgorBo

[EgorBo]

It looks like some (if not all) benchmarks are checked in as binaries there, so not sure it's even possible to port. I think we have a good coverage in microbenchmarks already indeed.