use inverter class to share values between

the two protocol instances of a proxy
- move forward_at_cmd_resp into class InverterG3P
- store inverter ptr in Solarman_V5 instances
- add inverter ptr to all constructurs of protocols
- adapt doku and unit tests-
- add integration tests for AT+ commands which
  check the forwarding from and to the TSUN cloud
-

app/src/gen3plus/infos_g3p.py

@@ -193,13 +193,12 @@ class RegisterSel:
 
 
 class InfosG3P(Infos):
-    __slots__ = ('client_mode', 'forward_at_cmd_resp')
+    __slots__ = ('client_mode')
 
     def __init__(self, client_mode: bool):
         super().__init__()
         self.client_mode = client_mode
         # shared value between both inverter connections
-        self.forward_at_cmd_resp = False
         '''Flag if response for the last at command must be send to the cloud.
 
            False: send result only to the MQTT broker, cause the AT+ command