[PhoneHub] Hide recent apps list if Apps setting is turned off.

Recent apps should be hidden entirely if a user disables the “Apps” row
in Chrome OS Settings. If a user later re-enables the “Apps” row, their
recent apps list should also restore.

and ash_unittests --gtest_filter="RecentAppButtonsViewTest*"

Bug: b/211938405
Test: ash_unittests --gtest_filter="RecentAppsInteractionHandlerTest*"
Change-Id: I7b0f36f27c8228224b20bcecf2cc87bb8e30ad64
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3358093
Reviewed-by: Jon Mann <jonmann@chromium.org>
Commit-Queue: Paulz Chen <paulzchen@google.com>
Cr-Commit-Position: refs/heads/main@{#955656}