fix: Safari picture-in-picture triggers fullscreenchange (5.x)

[mister-ben]

Description

When picture-in-picture mode is entered on Safari, webkitbeginfullscreen is triggered which results in a proxied fullscreenchange event and adding the fullscreen class to the player. That causes the tech element to collapse to zero height so that the "this video is playing in picture in picture" placeholder is not visible.

Specific Changes proposed

As with #4437 for v6, on webkitbeginfullscreen check whether the presentation mode is picture-in-picture' before proxying a fullscreenchange` event.

Requirements Checklist

• Feature implemented / Bug fixed
• Change has been verified in an actual browser (Chome, Firefox, IE)
• Reviewed by Two Core Contributors