build: Rename the names of the icons' files

The names of icons' files, besides containing the final names, they
also contained the path in which they were going to be installed.
This implies that they have to be renamed on the installation
process.

This patch creates the proper directory tree needed on the
installation process and renames all files' names to their final
names.

GNOME/gnome-photos!53
3 jobs for rename-icons in 15 minutes and 17 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Test
passed #187953
flatpak

00:14:37

 
  Review
passed #187954
review

00:00:40

manual #187955
allowed to fail manual
stop_review