Added sensor target VTS test

Initial submission of Sensor VTS test, including the following
test cases:

 * SensorListValid
 * NormalAccelerometerStreamingOperation
 * NormalGyroscopeStreamingOperation
 * AccelerometerSamplingPeriodHotSwitchOperation
 * AccelerometerBatchingOperation

One thing to note is that runtime has to be stopped to prevent
sensor service from stealing samples (which causes test failure).

Test: m vts -j32 &&
      adb shell stop &&
      vts-tradefed run commandAndExit vts \
          --skip-all-system-status-check \
          --primary-abi-only \
          --skip-preconditions \
          --module SensorsHidlTargetTest
      vts-tradefed run commandAndExit vts \
          --skip-all-system-status-check \
          --primary-abi-only \
          --skip-preconditions \
          --module SensorsHidlTest
      adb shell start

Test: # alternative, faster way to run target test only
      m sensors_hidl_hal_test -j32  &&
      TOUT=$T/out/target/product/${TARGET_PRODUCT}
      TEST=data/nativetest/sensors_hidl_hal_test/sensors_hidl_hal_test
      adb push ${TOUT}/${TEST} /${TEST} && \
      adb shell ${TEST}

Change-Id: I3e26aa550f4cdec2cebb847f47d63ed33a527210