some renaming and pedantic refactor

[adamsitnik]

this is my pedantic proposal to dotnet#174

When I was porting all the benchmarks to perf repo I realized that most of them have very long names, which are used as IDs in BenchView and don't look good in the web browser.

Before:

GuardedDevirtualizationThreeClass.Virtual.Call3
GuardedDevirtualizationThreeClassInterface.Interface.Call3
GuardedDevirtualizationTwoClass.Virtual.Call2
GuardedDevirtualizationTwoClassInterface.Interface.Call2

After:

GuardedDevirtualization.ThreeClassVirtual.Call
GuardedDevirtualization.ThreeClassInterface.Call
GuardedDevirtualization.TwoClassVirtual.Call
GuardedDevirtualization.TwoClassInterface.Call

Also instead of using Random we can use a ValuesGenerator which was added to perf repo to avoid common issues when working with random input.

@AndyAyersMS this PR is very subjective, if you don't like the changes please close it and I am going to merge dotnet#174 without it immediately.

[AndyAyersMS]

I didn't like the long names either so am happy to see them get shorter.