Add System.Threading.Thread to tests to restore missing types.
Upgrade System.Runtime dependency for JIT tests to get GCHandle.
Change system.runtime 4.0.20 to 4.1.0 rc2 dependency to try to copy the runtimes to CORE_ROOT.
Fix new project.json files.
Fix hardcoded Microsoft.DotNet.xunit.performance version.
Upgrade System.Runtime.InteropServices to prerelease level to avoid type conflicts with System.Runtime.
Commit migrated from https://github.com/dotnet/coreclr/commit/
a6b58c35d0652f49194782a80a7c5a63d432a9ff