Remove Search from the system Settings app DO NOT MERGE

The search settings acitivity lives in the system search app,
which is build-dependent. Also, since the Browser no longer
looks at the SHOW_WEB_SUGGESTIONS system preference, none
of the search settings affect the behavior of any other
platform apps.

The search settings will henceforth only be
available from within the search app (e.g. QuickSearchBox).

Bug: 3017365

Change-Id: I08f3979cd8cdc0742efbc49be95aa59753c94c0d