[Desktop] Do not blur or zoom the wallpaper during overlay expansion

This CL checks the boolean that indicates whether a blurred wallpaper
is supported. If not, do not blur or zoom the wallpaper during
overlay expansion.

This CL should not introduce any noticeable change to non-desktop
products.

Bug: 399112904
Flag: EXEMPT bugfix
Change-Id: I853717c5b8ec70a317ed67c7e3724782a6fa06b3