MultiHal 2.0 - setOperationMode and init direct channel flags

Implement setOperationMode method of HalProxy object and initialized the
direct channel flag for the sensors list. Also create some unit tests to
test both of these new additions in HalProxy_test.cpp.

Bug: 136511617
Test: Tested using unit tests and tested on device with both fake
      subhals

Change-Id: I4e39ca0e94b3e109706d628612d1db9c98aca053