Added System.Diagnostics.Process tests.

Added AssemblyInfo.cs file to Microsoft.Win32.Primitives, upped the version number to maximum. Tests dependent on this assembly and looking for any version of this assembly should be able to pick this up.
Fix dirs.proj to pick up csproj files that don't immediately exist under test directory but a level below.
@mellinoe I believe the catch block was added only to throw custom message with which the failing test could be identified. I'll leave it this way at this point.