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-errorlo

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>

show more ...

rtu: implement modbus sensor read

Read the modbus device config from the Entity Manager configuration and
create the sensor interfaces for related sensor register config.

Tested:
Added new Unit tes

rtu: implement modbus sensor read

Read the modbus device config from the Entity Manager configuration and
create the sensor interfaces for related sensor register config.

Tested:
Added new Unit test named test_sensors -
```
> meson test -t 10 -C builddir/ --print-errorlogs --wrapper="valgrind --error-exitcode=1" test_sensors
ninja: Entering directory `/host/repos/Modbus/phosphor-modbus/builddir'
[2/2] Linking target tests/test_sensors
1/1 test_sensors OK 13.98s

Ok: 1
Fail: 0
```

Tested on Qemu using Mock Modbus Device -
```
root@ventura:~# busctl tree xyz.openbmc_project.ModbusRTU
└─ /xyz
└─ /xyz/openbmc_project
├─ /xyz/openbmc_project/inventory_source
│ ├─ /xyz/openbmc_project/inventory_source/Heat_Exchanger_12_DevTTYUSB0
│ ├─ /xyz/openbmc_project/inventory_source/Heat_Exchanger_12_DevTTYUSB1
│ ├─ /xyz/openbmc_project/inventory_source/Reservoir_Pumping_Unit_12_DevTTYUSB0
│ └─ /xyz/openbmc_project/inventory_source/Reservoir_Pumping_Unit_12_DevTTYUSB1
└─ /xyz/openbmc_project/sensors
└─ /xyz/openbmc_project/sensors/temperature
├─ /xyz/openbmc_project/sensors/temperature/Reservoir_Pumping_Unit_12_DevTTYUSB0_RPU_Coolant_Inlet_Temp_C
├─ /xyz/openbmc_project/sensors/temperature/Reservoir_Pumping_Unit_12_DevTTYUSB0_RPU_Coolant_Outlet_Temp_C
├─ /xyz/openbmc_project/sensors/temperature/Reservoir_Pumping_Unit_12_DevTTYUSB1_RPU_Coolant_Inlet_Temp_C
└─ /xyz/openbmc_project/sensors/temperature/Reservoir_Pumping_Unit_12_DevTTYUSB1_RPU_Coolant_Outlet_Temp_C

busctl introspect xyz.openbmc_project.ModbusRTU /xyz/openbmc_project/sensors/temperature/Reservoir_Pumping_Unit_12_DevTTYUSB1_RPU_Coolant_Outlet_Temp_C
NAME TYPE SIGNATURE RESULT/VALUE FLAGS
org.freedesktop.DBus.Introspectable interface - - -
.Introspect method - s -
org.freedesktop.DBus.Peer interface - - -
.GetMachineId method - s -
.Ping method - - -
org.freedesktop.DBus.Properties interface - - -
.Get method ss v -
.GetAll method s a{sv} -
.Set method ssv - -
.PropertiesChanged signal sa{sv}as - -
xyz.openbmc_project.Sensor.Value interface - - -
.MaxValue property d nan emits-change writable
.MinValue property d nan emits-change writable
.Unit property s "xyz.openbmc_project.Sensor.Value.Unit.… emits-change writable
.Value property d 1670.6 emits-change writable
```

Change-Id: I1368e8df5999b5cee9ac19d185ee110a9ecc3021
Signed-off-by: Jagpal Singh Gill <paligill@gmail.com>

show more ...