regulators: Add Sensors to Services hierarchy

Add the Sensors service to the Services hierarchy:
* Add Sensors class to Services
* Add DBusSensors class to BMCServices
* Add MockSensors class to MockServices

Tested:
* DBusSensors
  * Acquired DBusSensors reference from BMCServices object
  * Successfully executed a sensor monitoring cycle using the reference
* MockSensors
  * Acquired MockSensors reference from MockServices object

Signed-off-by: Shawn McCarney <shawnmm@us.ibm.com>
Change-Id: Ida06baed47c0d8711ab3acba71f67df3646ea122
diff --git a/phosphor-regulators/test/mock_services.hpp b/phosphor-regulators/test/mock_services.hpp
index b121e13..8e3a100 100644
--- a/phosphor-regulators/test/mock_services.hpp
+++ b/phosphor-regulators/test/mock_services.hpp
@@ -20,8 +20,10 @@
 #include "mock_error_logging.hpp"
 #include "mock_journal.hpp"
 #include "mock_presence_service.hpp"
+#include "mock_sensors.hpp"
 #include "mock_vpd.hpp"
 #include "presence_service.hpp"
+#include "sensors.hpp"
 #include "services.hpp"
 #include "vpd.hpp"
 
@@ -70,6 +72,12 @@
         return presenceService;
     }
 
+    /** @copydoc Services::getSensors() */
+    virtual Sensors& getSensors() override
+    {
+        return sensors;
+    }
+
     /** @copydoc Services::getVPD() */
     virtual VPD& getVPD() override
     {
@@ -115,6 +123,18 @@
     }
 
     /**
+     * Returns the MockSensors object that implements the Sensors interface.
+     *
+     * This allows test cases to use the object in EXPECT_CALL() statements.
+     *
+     * @return mock sensors interface object
+     */
+    virtual MockSensors& getMockSensors()
+    {
+        return sensors;
+    }
+
+    /**
      * Returns the MockVPD object that implements the VPD interface.
      *
      * This allows test cases to use the object in EXPECT_CALL() statements.
@@ -148,6 +168,11 @@
     MockPresenceService presenceService{};
 
     /**
+     * Mock implementation of the Sensors interface.
+     */
+    MockSensors sensors{};
+
+    /**
      * Mock implementation of the VPD interface.
      */
     MockVPD vpd{};