Hydrotherm X8: flip operation_mode logic

turn_off/turn_on works better when operation_mode dp is a boolean, and the
modes are pulled from another dp, rather than the other way around.
The logic is simpler this way too.

custom_components/tuya_local/devices/hydrotherm_dynamic_x8_water_heater.yaml

@@ -4,11 +4,23 @@ primary_entity:
   dps:
     - id: 1
       type: boolean
-      name: power
-      hidden: true
+      name: operation_mode
       mapping:
         - dps_val: false
           value: "off"
+        - dps_val: true
+          constraint: work_mode
+          conditions:
+            - dps_val: ECO
+              value: eco
+            - dps_val: STANDARD
+              value: heat_pump
+            - dps_val: HYBRID
+              value: high_demand
+            - dps_val: HYBRID1
+              value: performance
+            - dps_val: ELEMENT
+              value: electric
     - id: 2
       type: integer
       name: temperature
@@ -21,44 +33,8 @@ primary_entity:
       name: current_temperature
     - id: 4
       type: string
-      name: operation_mode
-      mapping:
-        - dps_val: ECO
-          constraint: power
-          conditions:
-            - dps_val: false
-              value_redirect: power
-            - dps_val: true
-              value: eco
-        - dps_val: STANDARD
-          constraint: power
-          conditions:
-            - dps_val: false
-              value_redirect: power
-              value: "off"
-            - dps_val: true
-              value: heat_pump
-        - dps_val: HYBRID
-          constraint: power
-          conditions:
-            - dps_val: false
-              value_redirect: power
-            - dps_val: true
-              value: high_demand
-        - dps_val: HYBRID1
-          constraint: power
-          conditions:
-            - dps_val: false
-              value_redirect: power
-            - dps_val: true
-              value: performance
-        - dps_val: ELEMENT
-          constraint: power
-          conditions:
-            - dps_val: false
-              value_redirect: power
-            - dps_val: true
-              value: electric
+      name: work_mode
+      hidden: true
     - id: 21
       type: bitfield
       name: fault_code