Fix ANR SDK-3717

[piyush-kukadiya]

1. add threading annotation for ease of understanding like which method must run on which thread
2. add CtApiWrapper class to lazily initialize CtApi. Eager initialization of CtApi is causing ANR during CleverTapAPI instance creation triggered by DeviceId generation callback
3. add AnrWatchDog to sample app
4. remove isMainProcess check for xiaomi which is causing
5. fix failing test case and add new test cases