Add method to greylist

Add Landroid/hardware/camera2/CameraMetadata;->getNativeMetadataPtr()J
to greylist so that
CameraManagerTest#testCameraCharacteristicsNdkFromSdk no longer needs
to forego hidden api checks.

Bug: 149594233
Test: atest CameraManagerTest#testCameraCharacteristicsNdkFromSdk
Test: adb install -r -g CtsCameraTestCases.apk && \
      adb  shell am instrument -e class \
	'android.hardware.camera2.cts.CameraManagerTest#testCameraCharacteristicsNdkFromSdk' \
	-w 'android.camera.cts/androidx.test.runner.AndroidJUnitRunner'
Change-Id: Ibd53dd198efc5722e20f153ef5cc9433e5b7539d