Implement OtpManager in autofill.

This CL implements an OtpManager in components/autofill that will
replace the copy in.
components/password_manager/core/browser/one_time_passwords/

The OtpManager in Autofill is much simpler because it does not need to
track form structures like the old version. It can use
AutofillManager::Observer::OnFieldTypesDetermined() to learn when OTPs
need to be fetched and integrate into suggestion generation easily
because the fully classified FormStructure is available in Autofill.

Bug: 415273270
Change-Id: I6bb9be9fc46078f289eaf5d48587854573b9702a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6943295
Reviewed-by: Viktor Semeniuk <vsemeniuk@google.com>
Commit-Queue: Dominic Battré <battre@chromium.org>
Reviewed-by: Matthias Körber <koerber@google.com>
Cr-Commit-Position: refs/heads/main@{#1515550}