From launch to launch FPS from QCamera can be low/normal

From launch to launch FPS from QCamera can be low/normal on Linux. Low FPS is 1 FPS only.

This is very critical issue, in my opinion, in contrast with QTBUG-98925

I watch this issue very often on my machine.

I checked on WIndows, the same issue, but a little more stable. On WIndows FPS are ~10. Whereas camera gives (should give) 30 FPS.

On Linux 90% of launches are with 1 FPS, 9% with 15 FPS, and once I saw 30 FPS, as should be.