[3.0] demux: mp4: backport some patches from 4.0

The MP4 demuxer has evolved a lot in 4.0 and 3.0 is lagging. In particular it has some memory issues fixed by the last patch of this MR.

Dropped the newer patches that are not mine. It's mostly vlc_tick_t cleanup now.

Marked as draft until 3.0.19 is released as it doesn't fix any bug.

Draft as it relies on adding vlc_tick_t type+defines to the 3.0 branch to minimize changes when backporting patches which will be submitted separately.