Add a empty page to host Safety/emergency settings

The page will eventually be displayed on settings root. It's currently
disabled to avoid QA/dogfood confusion, as the page is pretty empty at
this point.

Bug: 175158310
Test: manual only. Skipped robolectric because the page is pretty empty.
      Will add more test as we build business logic.
Change-Id: I80f193f6e90b89ab0c37d0f23f7174e4ba86c091