regulators: Add configure support to Rail class

Implemented the configure() method in the Rail class.  This method
applies any configuration changes that are defined for the rail.

Also added a few missing #includes in the configuration_tests.cpp file.

Signed-off-by: Shawn McCarney <shawnmm@us.ibm.com>
Change-Id: I4164621f6d599bbf1417ebb9328a35bd2b2d656e
diff --git a/phosphor-regulators/test/configuration_tests.cpp b/phosphor-regulators/test/configuration_tests.cpp
index 0865be7..a7ba37f 100644
--- a/phosphor-regulators/test/configuration_tests.cpp
+++ b/phosphor-regulators/test/configuration_tests.cpp
@@ -25,9 +25,12 @@
 #include "mocked_i2c_interface.hpp"
 #include "pmbus_utils.hpp"
 #include "pmbus_write_vout_command_action.hpp"
+#include "presence_detection.hpp"
 #include "rail.hpp"
+#include "rule.hpp"
 #include "system.hpp"
 
+#include <cstdint>
 #include <memory>
 #include <optional>
 #include <utility>