Adds check_interface_{restart,start,stop} check_builtins.

Includes refactoring out interface inheritance hierarchy logic to a new
interface_utils file.

Bug: 137397100
Test: 'm' with an init_rc that misspells an interface in an
interface_start, interface_restart, or interface_stop line.
Change-Id: I9f650289d64ae2b13435a81e1693c7ab5e6e9ecf