Added new device configuration for Omni X Duplex Water Heater in the … (#5390)

* Added new device configuration for Omni X Duplex Water Heater in the Tuya Local custom component.

* changes as requested.

* feat(omni_x_duplex_waterheater): simplify operation_mode

Basically mode should never change for this model, so do not change it together with operation mode. Instead leave it as a
read-only attribute.

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Co-authored-by: Jason Rumney <make-all@users.noreply.github.com>

custom_components/tuya_local/devices/omni_x_duplex_waterheater.yaml

@@ -0,0 +1,43 @@
+name: Water heater
+products:
+  - id: 5qklaasyaemcifen
+    manufacturer: Omni X
+    model: Duplex
+entities:
+  - entity: water_heater
+    dps:
+      - id: 1
+        type: boolean
+        name: operation_mode
+        mapping:
+          - dps_val: false
+            value: "off"
+          - dps_val: true
+            value: heat_pump
+      - id: 2
+        type: string
+        name: unused_mode  # should be hot always for this model
+      - id: 4
+        type: integer
+        name: temperature
+        unit: C
+        range:
+          min: 35
+          max: 60
+      - id: 16
+        type: integer
+        name: current_temperature
+  - entity: binary_sensor
+    class: problem
+    category: diagnostic
+    dps:
+      - id: 15
+        type: bitfield
+        name: sensor
+        mapping:
+          - dps_val: 0
+            value: false
+          - value: true
+      - id: 15
+        type: bitfield
+        name: fault_code