GetBuildNameForPerfTesting

This will return the name specified with -BuildName=SomeName (needs to be a valid c++ name a-z A-Z _ 0-9 so we don't run into issues when we pass it around) or if not specified "CL%d" where d is coming from [GetChangeListNumberForPerfTesting()](API\Runtime\Core\ProfilingDebugging\GetChangeListNumberForPerfTestin-)