Update the webauthn account chooser UI

This change prettifies the account chooser UI by implementing a version of the
hover list instead of a table view.

I'm planning to add user icons in a follow up patch to keep CL sizes low.

For app/generated_resources:
TBR=cpu@chromium.org

Bug: 955439
Change-Id: I104b5db352eef7fb143ef74cb3cc5d2c1afd98cb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1577989
Commit-Queue: Nina Satragno <nsatragno@chromium.org>
Reviewed-by: Martin Kreichgauer <martinkr@google.com>
Cr-Commit-Position: refs/heads/master@{#654020}
17 files changed