[Android 8.0+] Add Android Picture in Picture support

With the latest Android Q beta release, apps installed outside the play store have their Screen Overlay permission revoked in 30 seconds after enabling them. This is to track down and stop shady apk apps which abuse the screen overlay option and get users to click on things they didn't mean to, malware etc. More info in article below

https://www.androidpolice.com/2019/03/16/android-q-steps-up-the-fight-up-against-overlay-based-malware/

Problem is, NewPipe uses screen overlay for the popup and having to re-enable the permission every time a new popup video is being played... The ideal solution is to switch to the native PIP mode from Oreo API 26 and up, and leave the existing floating player code for Android Nougat and older.

https://developer.android.com/guide/topics/ui/picture-in-picture

Slowly as dev time goes on and more users move to Oreo and higher, the floating player method can switch to PIP completely.