HDR10: verify that static metadata change is propogated to display with 0 latency

And that it does not cause any memory leaks or crashes, like it does https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/issues/727#note_823124

See https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/issues/875

I will point out that ffrobe sees it on pkt_pos=7258705: side_data_type=Content light level metadata max_content=284 max_average=145 to side_data_type=Content light level metadata max_content=378 max_average=277

HDR10 CLL (not MDCV) can change per segment on Blu-rays or even arbitrary in mp4's. This is mandated in CTA-861-G (and now -H).

Moreover when Apple TV 4K derives HDR10 stream from Dolby Vision profile 5 IPTPQc2 colorspace (after all the contant luminance/ constant intensity can be mostly preserved if using R'G'B' and it does apply MMR on profile 5, not on 8 alas).

Sample is here https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/uploads/16c628c535865d7282a48317064345a2/out.mp4

I suppose I can generate actual change of content CLL in more crazy manner.