Controlbar fading for instream mode in release-6.9 [Delivers #70673788]

Relates to these
https://github.com/jwplayer/jwplayer/commit/0f225f1199cc6453c7f0310bf2218814a41bdc00
https://github.com/jwplayer/jwplayer/commit/893aee310471d19d072da2bb30a6ae03e2641faa
https://github.com/jwplayer/jwplayer/commit/55b2870754b6d4dba8b29e2463e665628c76738a
As a general rule,  always keep a reference and clear timeouts before starting them, so only one can run at once. A debounce method would be handy.