test: pid: zone

Add unit-tests for the PID zone module.
Add zone_mock.

Tested: Ran on quanta-q71l board and it behaved as expected.

Change-Id: I51185b2d2daacea6ffb687e8f38c4fe2b2a1bed3
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/pid/thermalcontroller.cpp b/pid/thermalcontroller.cpp
index 61e5ca9..dee2d4e 100644
--- a/pid/thermalcontroller.cpp
+++ b/pid/thermalcontroller.cpp
@@ -20,7 +20,7 @@
 
 
 std::unique_ptr<PIDController> ThermalController::CreateThermalPid(
-    PIDZone* owner,
+    ZoneInterface* owner,
     const std::string& id,
     std::vector<std::string>& inputs,
     float setpoint,