[ios] Add password generation UI

Also, modified slightly action_sheet_coordinator to allow selecting style of UIAlertController.

Bug: 886583
Change-Id: Icc57b96b8a4033d872d373414a06af0e905b6ca7
Reviewed-on: https://chromium-review.googlesource.com/c/1375950
Commit-Queue: David Jean <djean@chromium.org>
Reviewed-by: Vadym Doroshenko <dvadym@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#617460}
4 files changed