platform-mc: Create Numeric sensor D-Bus object

Added numeric_sensor class. The NumericSensor class will create the
Numeric sensor D-Bus object. The class also handles sensor status and
exports its status to D-Bus interfaces.

tested: Verified on ast2600 EVB which is connected to a PLDM device
over I2C. bmcweb can display the state of numeric sensor.

Signed-off-by: Thu Nguyen <thu@os.amperecomputing.com>
Change-Id: I1c7de2e74100ed787ed2119896d3c5b36098dd96
diff --git a/platform-mc/test/meson.build b/platform-mc/test/meson.build
index 8c4f570..6b95f90 100644
--- a/platform-mc/test/meson.build
+++ b/platform-mc/test/meson.build
@@ -4,6 +4,7 @@
             '../terminus.cpp',
             '../platform_manager.cpp',
             '../manager.cpp',
+            '../numeric_sensor.cpp',
             '../../requester/mctp_endpoint_discovery.cpp'],
             include_directories: ['../../requester', '../../pldmd'])