Add Amber to meson.build

See merge request GNOME/gnome-backgrounds!17

start with jpeg xl early in the cycle again to potentially be able to
address stability and performance issues.

See
https://gitlab.gnome.org/GNOME/gnome-build-meta/-/issues/703
https://gitlab.gnome.org/GNOME/gnome-build-meta/-/issues/502
https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/6886
https://gitlab.gnome.org/GNOME/gnome-build-meta/-/issues/698#note_1812452

- placeholder for now

- adjust composition to look decent at 16:9 but fine when cropped in for ultrawides

Refresh Amber for 46

See merge request GNOME/gnome-backgrounds!18

- refresh also means pruning.

more pruning

- when the nostalgia wears off, nothing is left

- remove geo4, too similar to the rounded rectangles.
- rename the ring

- reframe and relight the geometrics 3 variant into a new asset

- use JXL

- use JXL

- denoiser didn't quite work on the subsurface of the pills

- (not) the first iteration of the 46 default

- forgot to add the files :/

- dark variant perhaps too contrasty and detailed

- while finetuning, resort to a simpler rendering

- minor improvements in terms of color/bounced light

- still a bit mushed on the unfocused glass bits

- updates the set of icons, no dots this time