Set basic SVG attributes (bug#40845)

Set basic SVG attributes (bug#40845)

* test/manual/image-transforms-tests.el: Replace hard-coded colors
with defaults.
* src/dispextern.h (struct image):
* src/image.c (search_image_cache):
(xbm_load_image):
(xbm_load):
(pbm_load): Rename from frame to face where relevant.
(svg_load_image): Parse the image to find out the size, then wrap it
in another SVG to set a new size and colors, etc.
(lookup_image): Use the face colors instead of the frame colors.
(search_image_cache): Add ability to ignore the face colors.
(uncache_image): Uncache all copies of the image that share the spec,
even if the face colors don't match.
* etc/NEWS: Describe the changes.