Add Sensors Multihal support for Hal 2.0

The multihal framework is a HAL interface for the sensors framework that
allows multiple vendors to package their HAL implementation into a
subHAL dynamic library that will be loaded and used to pass on method
calls to the appropriate subHAL. The HalProxy object, that will act as
the main proxy sensors wrapper for the multiHAL handles writing sensor
events to the event FMQ and wakelock acquisition and releasing via a
callback object it passes to the subHALs.

In order to turn your HAL 2.0 executable into a subHAL to be used by the
multiHAL, implement the Return<Result> initialize(sp<HalProxyCallback>&
callback) method of the ISensorsSubHal derived class. Implement the
ISensorsSubHal* sensorsHalGetSubHal(uint32_t* version)method and have it
return a pointer to your subHAL object. Build this into a dynamic
library and list its filename under /vendor/etc/sensors/hals.conf.

Squashed commits:

07b442e9 (refs/published/mh2_2) MH2 | Write processedEvents instead of
original events.
b38f2e25 Merge "MH2 | Check that subhal index is in range"
d38f9947 Merge "MH2 | Implement debug method of HalProxy"
bf46132f (refs/published/mh2_4, mh2_4) MH2 | Implement debug method of
HalProxy
1de5bb33 MH2 | Fix wakelock name
e0721534 (refs/published/mh2_3, mh2_3) MH2 | Check that subhal index is
in range
336c1c71 MH2 | Add restart logic in HalProxy::initialize method.
731d7125 MH2 | Change rc file to more appropriate settings
f09465d1 MH2 | Add makeFMQ helpers to HalProxy_test
75cc7bf2 MH2 | Implement wakelock processing thread
e93fdf9a MH2 | Implement dynamic sensors callbacks on HalProxy
82b84148 Remove libhwbinder/libhidltransport deps
d45e49b4 Merge "MH2 | Implement pending writes thread"
59714269 MH2 | Implement pending writes thread
db23aa82 MH2 | Implement direct channel and direct report methods
83e4370a MH2 | Implement injectSensorData method of HalProxy
d0cd57d4 MH2 | Implement ScopeWakelock ctor and dtor
537c0274 MH2 | Add rough proxy callback postEvents method
f97a3f35 Multihal 2.0 - Small tweaks to sensorHandle handling
7a723546 MultiHal 2.0 - setOperationMode and init direct channel flags
dc7a8e78 MultiHal 2.0 - Get sensors list from subhals
4b4c7b74 MultiHal 2.0 - activate, batch, flush methods of HalProxy
1638531d MultiHal 2.0 - proxying api calls helper methods
aacbf948 Set up shell to use for unit tests
2879067d Multihal 2.0 - Implement SubHal discovery
c34e6683 Add a sub-HAL implementation for testing multi-HAL
a689f8a6 Add skeleton for multihal 2.0

Bug: 136511617
Test: atest android.hardware.sensors@2.0-halproxy-unit-tests &&
vts-tradefed run commandAndExit vts --skip-all-system-status-check
--primary-abi-only --skip-preconditions --module VtsHalSensorsV2_0Target

Change-Id: Ibe92d40c92b70848526b0e941bbcffbaf81ffaf2