It's been on since M49. Also moved tests from harmony -> es6,
one of which was merged with another test of the same name.
While moving stuff over to regexp.js, I also noticed that there
were unused calls to %FunctionSetName and %SetNativeFlag (those
calls are already handled by InstallGetter()).
Review URL: https://codereview.chromium.org/1838563003
Cr-Commit-Position: refs/heads/master@{#35076}
