[iOS]Ensure expectations are followed by a verify

This also ensure that mocks are better typed.

This was part of the reverted CL crrev.com/c/6618757. The `OCMExpect`
was replaced by a `OCMStub`, given that it seems that the URL method is
only called sometime and not always, as seen in the test result of
https://ci.chromium.org/ui/p/chromium/builders/ci/ios-asan/90850/overview

Bug: 421873301
Change-Id: I95e261e14249dc8dc8308c36516cb79f872bff29
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6632601
Commit-Queue: Arthur Milchior <arthurmilchior@chromium.org>
Reviewed-by: Mike Dougherty <michaeldo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1473601}