ContentSettings: Migrate content settings observers

Multiple content settings providers use ContentSettingsType::DEFAULT
to indicate that any setting might have changes. Many observers don't
handle this case correctly.

We added a wrapper class for ContentSettingsType that enforces
correctly checking whether the type an observer cares about is affected.

Bug: 1245927
Change-Id: Ia14d0c1318e877d61c823bf3d9d67991dfd89467
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3243948
Reviewed-by: Peter Beverloo <peter@chromium.org>
Reviewed-by: Raymes Khoury <raymes@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Reviewed-by: Eugene Zemtsov <eugene@chromium.org>
Commit-Queue: Christian Dullweber <dullweber@chromium.org>
Cr-Commit-Position: refs/heads/main@{#935380}