rtu: add read status register and event support

Add support to read the status registers and generate the appropriate
events.

Tested:
Unit Test -
```
> meson test -t 10 -C builddir/ --print-errorlogs --wrapper="valgrind --error-exitcode=1" test_events
ninja: Entering directory `/host/repos/Modbus/phosphor-modbus/builddir'
ninja: no work to do.
1/1 test_events        OK               9.69s

Ok:                1
Fail:              0
```

Tested on Qemu -
```
Apr 03 15:41:52 ventura phosphor-modbus-rtu[1654]: OPENBMC_MESSAGE_ID={"xyz.openbmc_project.Sensor.SensorFailure":{"SENSOR_NAME":"/xyz/openbmc_project/sensors/RPU_Coolant_Outlet_Thermometer_Status","_SOURCE":{"COLUMN":73,"FILE":"../git/common/ev
ents.cpp","FUNCTION":"sdbusplus::async::task<> phosphor::modbus::events::Events::generateSensorFailureEvent(sdbusplus::message::object_path, bool)","LINE":95,"PID":1654}}}
...
Apr 03 15:41:52 ventura phosphor-modbus-rtu[1654]: OPENBMC_MESSAGE_ID={"xyz.openbmc_project.Sensor.Threshold.ReadingCritical":{"READING_VALUE":1670.6000000000001,"SENSOR_NAME":"/xyz/openbmc_project/sensors/RPU_Coolant_Outlet_Temp_C","UNITS":"xyz
.openbmc_project.Sensor.Value.Unit.DegreesC","_SOURCE":{"COLUMN":67,"FILE":"../git/common/events.cpp","FUNCTION":"sdbusplus::async::task<> phosphor::modbus::events::Events::generateSensorReadingEvent(sdbusplus::message::object_path, phosphor::modbus::events::EventLevel, double, sdbusplus::common::xyz::openbmc_project::sensor::Value::Unit, bool)","LINE":48,"PID":1654}}}
```

Change-Id: Icd78f22cf07798d06916cc077ec3f8bfac9ee8d3
Signed-off-by: Jagpal Singh Gill <paligill@gmail.com>
diff --git a/tests/test_sensors.cpp b/tests/test_sensors.cpp
index a5046b0..a6574cb 100644
--- a/tests/test_sensors.cpp
+++ b/tests/test_sensors.cpp
@@ -1,3 +1,4 @@
+#include "common/events.hpp"
 #include "device/device_factory.hpp"
 #include "modbus_server_tester.hpp"
 #include "port/base_port.hpp"
@@ -22,6 +23,7 @@
 namespace PortConfigIntf = PortIntf::config;
 namespace DeviceIntf = phosphor::modbus::rtu::device;
 namespace DeviceConfigIntf = DeviceIntf::config;
+namespace EventIntf = phosphor::modbus::events;
 
 class MockPort : public PortIntf::BasePort
 {
@@ -134,11 +136,12 @@
             DeviceConfigIntf::DeviceModel::RDF040DSS5193E0,
         };
 
-        auto mockPort =
-            std::make_unique<MockPort>(ctx, portConfig, clientDevicePath);
+        EventIntf::Events events{ctx};
+
+        MockPort mockPort(ctx, portConfig, clientDevicePath);
 
         auto device = DeviceIntf::DeviceFactory::create(
-            ctx, deviceFactoryConfig, *mockPort);
+            ctx, deviceFactoryConfig, mockPort, events);
 
         co_await device->readSensorRegisters();