BouncyBall: Prefer to run the test at 60Hz

Many devices default to higher resolutions than 60Hz.  We have
our app prefer 60Hz, if it's available.  Otherwise, we test with
the lowest refresh rate above 60Hz.  If the device doesn't support
at least 60Hz, we abort in failure.

Bug: 408044970
Test: Locally ran on 90Hz device, which dialed back to 60Hz for this; tried on 60Hz device; tried on default 60Hz device supporting 90Hz with DESIRED_FRAME_RATE hacked to 80 and it switched to 90Hz; tried on device supporting max 90Hz with DESIRED_FRAME_RATE hacked to 100 and it aborted.
Flag: EXEMPT for test app
Change-Id: I2a7400931af2f842fb5865622ff4a48089caae08