GLConsumer: add build-time disable of gpu protected content

Some drivers incorrectly claim support for EGL_EXT_protected_content.
Until we've been able to verify that devices which claim support
actually implement it properly, require that GPU access to protected
content be manually enabled per-device.

Bug: 28545166
Change-Id: Ic10e47a99c38737ce1c39439fe9347d628aec491