regulators: Add inventory path to Chassis class

A previous commit added the "inventory_path" property to the "chassis"
object in the JSON configuration file.

This commit adds that new property to the C++ implementation:
* Chassis class and associated gtests
* JSON configuration file parser functions and associated gtests
* Other gtests affected by the change to the Chassis constructor

Signed-off-by: Shawn McCarney <shawnmm@us.ibm.com>
Change-Id: I7406f874263d01e6faa2b8c333cb1baf915cf2ac
diff --git a/phosphor-regulators/test/presence_detection_tests.cpp b/phosphor-regulators/test/presence_detection_tests.cpp
index e89af2c..c63f403 100644
--- a/phosphor-regulators/test/presence_detection_tests.cpp
+++ b/phosphor-regulators/test/presence_detection_tests.cpp
@@ -107,8 +107,8 @@
     // Create Chassis that contains Device
     std::vector<std::unique_ptr<Device>> devices{};
     devices.emplace_back(std::move(device));
-    std::unique_ptr<Chassis> chassis =
-        std::make_unique<Chassis>(1, std::move(devices));
+    std::unique_ptr<Chassis> chassis = std::make_unique<Chassis>(
+        1, "/xyz/openbmc_project/inventory/system/chassis", std::move(devices));
     Chassis* chassisPtr = chassis.get();
 
     // Create System that contains Chassis