[iOS][Mim2]Sends continuation to change profile handler

This CL ensures that the Change Profile Handler receive a continuation
that is decided by the place the Signin flow was first started.

In order to do that, the AuthenticationFlow now takes a delegate.

This delegate declares two different methods. One for signin in the same
profile and one in a different profile. Given that the delegate is
stopped when the profile is tear down, the delegate is informed that it
must not interrupt the AuthenticationFlow.

Some actions should be done before the profile switch occurs. Such as
closing the current tab if it’s sent to the managed account. This will
be done in a future CL.

Bug: 375605572
Change-Id: I89fd798578a1e6f4b9e6b665f1c2c5160017a5b8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6383098
Commit-Queue: Arthur Milchior <arthurmilchior@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Auto-Submit: Arthur Milchior <arthurmilchior@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1445239}