Add media-libs/openh264 to dev and test images

This CL adds media-libs/openh264 to the CrOS dev/test images.
Openh264 generates two command line utilities (openh264dec and
openh264enc), both to be used by Tast tests to manipulate h264
files from the command line (crrev.com/c/2588370).  Total extra
added size : 8.1M

This CL also sets the USE flag |utils| to build+install said
utilities.

BUG=b:174103282
TEST=CQ

Change-Id: If94ac51c1f0341ce01167c11dd90c64469069b3a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/chromiumos-overlay/+/2587242
Tested-by: Miguel Casas <mcasas@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Andres Calderon Jaramillo <andrescj@google.com>
Commit-Queue: Miguel Casas <mcasas@chromium.org>
3 files changed