print full architecture name

[adamsitnik]

@AndreyAkinshin I've recently been running a lot of benchmarks for x64, x86, ARM and ARM64. The reported results always contained "64bit" or "32bit" which does not tell if it's ARM or not. I think that we should use full architecture name.

Before:

BenchmarkDotNet=v0.11.5.20190727-develop, OS=Windows 10.0.18362
Intel Xeon CPU E5-1650 v4 3.60GHz, 1 CPU, 12 logical and 6 physical cores
  [Host]     : .NET Framework 4.8 (4.8.3815.0), 64bit RyuJIT
  DefaultJob : .NET Framework 4.8 (4.8.3815.0), 64bit RyuJIT

After:

BenchmarkDotNet=v0.11.5.20190727-develop, OS=Windows 10.0.18362
Intel Xeon CPU E5-1650 v4 3.60GHz, 1 CPU, 12 logical and 6 physical cores
  [Host]     : .NET Framework 4.8 (4.8.3815.0), X64 RyuJIT
  DefaultJob : .NET Framework 4.8 (4.8.3815.0), X64 RyuJIT