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}