cabana: Improve seeking and zooming

[deanlee]

resolve https://github.com/commaai/openpilot/discussions/26091#discussioncomment-9289543 :

1. Immediately update the timeline to the current seeked-to time after seeking.
2. Improve camera caching by storing decoded frames within a 2-second window. This significantly boosts performance, especially when zooming into short time ranges, as frames can be retrieved from the cache instead of being decoded with ffmpeg.
3. Immediately return after calling seekTo() in ChartsWidget::updateState() to prevent drawing incorrect timelines in Chart::updatePlot().

The comparison after zooming in to 100 milliseconds (Real-time recording) :
before (Seems stuck because of camera blocking and incorrect updatePlot, though it's not truly hanging) :

Kazam_screencast_00145.webm

after:

Kazam_screencast_00144.webm

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[sshane]

fyi I also had hanging when zooming in with wide ranges (~minutes), which seems fixed with this!

[sshane]

I noticed I can't press the back mouse button nearly as quickly to zoom out any more. It would also be nice to allow redo zoom actions with the forward mouse button (though not necessarily in this PR!)

[deanlee]

I noticed I can't press the back mouse button nearly as quickly to zoom out any more. It would also be nice to allow redo zoom actions with the forward mouse button (though not necessarily in this PR!)

Since I don't have a back button on my mouse right now, I can't check it. But from what I can see, there don't seem to be any issues that would cause the back button to stop working (This part of the code has never been changed). I suggest adding support for the forward button and fixing any possible issues with the back button in a separate PR.