Fix installing WebAPK with SVG icon

Installing WebAPK with SVG icon always failed because there is no
preferred size specified when downloading the SVG icon and it result
in an empty Bitmap and returns an error.

This CL creates a "WebappIcon" class that contains the url, purpose,
and usage of the icon. The purpose and usage are used to decide the
ideal size of it.

Bug: 1428668, 1444216
Change-Id: Ia0301ea7fef51b9a58d9fb9b217aed30e207fa0d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4519242


Auto-Submit: Ella Ge <eirage@chromium.org>
Reviewed-by: Rayan Kanso <rayankans@chromium.org>
Commit-Queue: Rayan Kanso <rayankans@chromium.org>
Reviewed-by: Glenn Hartmann <hartmanng@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1143947}