QVideoFrame: harden ctor from QHwVideoBuffer


In general `QHwVideoBuffer` needs to go through
`QVideoFramePrivate::createFrame` and `QHwVideoBuffer::format()` is
expected to be invalid. We're now enforcing it.
Furthermore we tighten the used templates with concepts.

Pick-to: 6.12
Change-Id: Ie6c58bd04d7f7a1a102fe9467ef6220a8dd932ba
Reviewed-by: Artem Dyomin <artem.dyomin@qt.io>
commit5b44993c863675b6b9c40a168cde5de4d64aac4c
parentaeadc3b96740798689353fb9936240e703824e3c
authorTim Blechmann <tim.blechmann@qt.io>
committerTim Blechmann <tim.blechmann@qt.io>
commit timeMon, 19 Oct 2026 04:05:10 +0000