Create separate VTS target for Sensors HAL 2.1

Dependencies don't use cflags set by code that depends on them so the
VTS test for HAL 2.1 wasn't properly pulling the 2.1 interface when
present on the device (it was using the 2.0 interface). Modify the
Android.bp files to define the right flags depending on whether we're
testing HAL 2.0 or 2.1.

Bug: 149759782
Test: atest VtsHalSensorsV2_0TargetTest VtsHalSensorsV2_1TargetTest
Change-Id: I3533b6c244e767a8defe0a44a14025fdeb8eeeba