Add DescramberTests in Tuner VTS

Note that this test also includes MediaCasService openSession test
to pass the session id as the key token to the IDescrambler

Test: atest VtsHalTvTunerV1_0TargetTest
Bug: 150987138
Change-Id: Iacd4ad5fcd957a6e3bb4a5730337ecaa3adc0aa2