MetadataParser: Move relocation code to the thumbnail class.

To avoid having assumptions about the naming scheme of thumbnails
outside of the associated class.
4 jobs for fix_thumbnail_relocation in 12 minutes and 16 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #288943
amd64 debian
asan-ubsan

00:11:20

passed #288940
amd64 debian
linux

00:10:22

passed #288941
win32
win32

00:12:16

passed #288942
win64
win64

00:09:56