HTML <permission> requests get ignored -> no microphone/video on Zoom/Meet

Both Zoom and Google Meet seem to use the new HTML <permission> element if the browser advertises support for it.

However, permission requests seem to be silently ignored by QtWebEngine, leading to webcam/microphone not being possible to enable on e.g. Google Meet (New meeting -> Start an instant meeting) or [Zoom](https://zoom.us/test) (join -> join from your browser -> Use microphone and camera), both tested with simplebrowser.

Simpler demo page: [permission.site (permission element)](https://permission.site/pepc.html)

Clicking the button a few times shows "The permission element already has a request in progress." in the devtools console.

Passing QTWEBENGINE_CHROMIUM_FLAGS=--disable-features=PermissionElement makes things work, like they do on Qt 6.8.3 too.