p13n: browser tests for wallpaper info syncing

Add negative and positive tests for different wallpaper infos to verify
the syncing in flow.

BUG=b:324919452
TEST=browser_tests --gtest_filter="*WallpaperInfoBrowserTest*"

Cq-Include-Trybots: luci.chrome.try:linux-chromeos-chrome
Change-Id: I94960cfa5c8496f11009a9bd9e57a694724bbb2b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5411221


Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Commit-Queue: Jason Thai <jasontt@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1283478}