CTS tests for Voice Settings: ZenMode, BatterSaverMode, Airplane Mode

1. There are 3 CTS tests: one for each of the modes  ZenMode, BatterSaverMode, Airplane Mode.
2. In each test, there are 2 testcases. One to set the mode ON. And the
other to set it to OFF.
3. First testcase run in a test depends on the current setting value of the mode.
   Fir example, if it is currently set to OFF, testcase to set the mode to ON is run first.
   Once it completes successfully, a testcase to set the mode back to
   OFF is run.

Design details
==============
1. The various activities/services involved are:
     1.1. CTS_Test starts TestStartActivity
     1.2. That starts VoiceInteractionMain
     1.3. That starts MainInteractionService (the voice_interaction_service)
     1.4. That starts MainInteractionSession
     1.5. which fires an intent, based on the given test case type, to handle one of the following 3 activities:
         Zen Mode
         Airplane Mode
         BatterySaver Mode
2. Each of the 3 tests is a separate CTS test - so for each of the
tests, the above chain is started and is terminated at tne end of the
test.

3. Each test has 2 testcases. For each of the 2 testcases, new chain
starting with step 1.2 is initiated; i.e., each testcase is handled by a
separate VoiceInteractionSession (= MainInteractionSession in this
case).

Change-Id: I4c0ac753ceca845c82ade5064fbe1265ff071daf
22 files changed