Update performance tests

Update performance tests

Add inner iterations to all performance tests in the perflab directory.
This is because we were measuring a time that was to small, and the
results were not useful.  This should also reduce the number of high level
iterations we run as well.

Commit migrated from https://github.com/dotnet/coreclr/commit/e265939060ae690a3e971d80d60cdb5b45f734bb