Render 48x48 choice screen images (scaled down to 24x24) irrespective of 'percent'.

Having a `srcset` with x1/x2 sizes doesn't make much sense if the image bytes do not go over the wire.

Also updates the Google favicon to one that offers at least 48x48 resolutions.

Overall this saves 40KiB with an overall better display quality of the icons.

Bug: b/304719922
Change-Id: Ifa558e388439d9ae2e17a21aa42d3614dac2e08a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4931153
Commit-Queue: Jens Mueller <muellerj@google.com>
Auto-Submit: Jens Mueller <muellerj@google.com>
Reviewed-by: Orin Jaworski <orinj@chromium.org>
Reviewed-by: Nicolas Dossou-Gbété <dgn@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1208721}