[modbus_controller] courtesy response (#10027)

Co-authored-by: Jesse Hills <3060199+jesserockz@users.noreply.github.com>
Co-authored-by: pre-commit-ci-lite[bot] <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>

tests/components/modbus_controller/common.yaml

@@ -45,6 +45,22 @@ modbus_controller:
           printf("address=%d, value=%d", x);
           return true;
     max_cmd_retries: 0
+  - id: modbus_controller4
+    modbus_id: mod_bus2
+    address: 0x4
+    server_courtesy_response:
+      enabled: true
+      register_last_address: 100
+      register_value: 0
+    server_registers:
+      - address: 0x0001
+        value_type: U_WORD
+        read_lambda: |-
+          return 0x8;
+      - address: 0x0005
+        value_type: U_WORD
+        read_lambda: |-
+          return (random_uint32() % 100);
 binary_sensor:
   - platform: modbus_controller
     modbus_controller_id: modbus_controller1