Fade in layer surfaces

Makes e.g. the screen lock a bit smoother
2 jobs for fade-in-layers in 3 minutes and 26 seconds (queued for 3 minutes and 6 seconds)
latest
Status Job ID Name Coverage
  Build
passed #974
librem5
build-with-xwayland

00:01:42

passed #975
librem5
build-without-xwayland

00:01:44