Source of the XMP data is our MP data, should be the original XMP when present

[PetrVys]

The way the program approaches merging XMP is that it creates full XMP data for MotionPhoto and then tries to copy relevant tags and elements from the original image file into it if possible.

Unfortunately this sometimes creates issues, most often with namespace aliases.

When the source image has XMP, the order should be switched around. This requires sanitizing the output of exiftool's XMP - sometimes it contains binary garbage after the end of XML.

We should take only data between <x:xmpmeta and </x:xmpmeta> and create relevant attributes and filled Directory structure inside.