[ios] Cleanup in select_profile_intent.swift

This CL contains some minor cleanup in widgets code:
 - avatarForProfile renamed to avatarForAccount (since its logic is per
   account and not per profile)
 - Removes init code from WidgetConfigurationIntent because not used

Bug: 376679167
Change-Id: I9ed601e680612d9887e9ebef16dd237b2cea82e0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6281950
Reviewed-by: Mark Cogan <marq@chromium.org>
Commit-Queue: Mark Cogan <marq@chromium.org>
Commit-Queue: Federica Germinario <fedegermi@google.com>
Auto-Submit: Federica Germinario <fedegermi@google.com>
Cr-Commit-Position: refs/heads/main@{#1422997}