Move html case up since it is the most likely to be hit
Use plain string comparison which is twice as fast
Avoid strtolower call at every twig_escape_filter call
Add UTF-8 in uppercase since it is so common
Use uppercased charsets consistently (as in js/css/html_attr strategies)
Avoid unnecessary is_object call
Make happy path (strings) faster by avoiding the cast, same perfs for the other cases