[iOS] Add accounts sections to AccountsTableViewController

This CL adds the view title, and adds a section for each available
identity.
Each section has the identity details item, and a button to remove this
identity. The button to remove account is not actionable yet, later CLs
will add this logic.

screenshot in crbug.com/349071402#comment3

Low-Coverage-Reason: TESTS_IN_SEPARATE_CL
Bug: 349071402
Change-Id: I54e93a1a9422a6d4edbd7b0d10ad1330a25e4845
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5756601
Commit-Queue: Jood Hajeer <jood@google.com>
Reviewed-by: Jérôme Lebel <jlebel@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1337773}