Turn on integer overflow sanitization for libui.

This re-enables integer overflow sanitization for the libui library.
This used to be enabled as the broader 'integer' setting, but was
turned off when Gralloc1On0Adapter.cpp was added. This file no longer
exists so there should be no problem re-enabling integer overflow
sanitization.

Test: Pixel booted. No runtime errors thrown when in diagnostics mode.
Bug: 63759345
Change-Id: I70dcc15143075a01082386ac3ab3f8de586f6ee4