Working on a python example plus fixing python grpc code (#6456)

Refactored python grpc code gen

Adds example server & client + fixes ci

Fixes generated code

Making sure we encode the reply string as utf8

Adds Readme details to clarify issue regarding encoding when python is sending/receiving

grpc/examples/python/greeter/models/greeter_grpc_fb.py

@@ -0,0 +1,52 @@
+# Generated by the gRPC Python protocol compiler plugin. DO NOT EDIT!
+
+import grpc
+
+class GreeterStub(object):
+  """ Interface exported by the server. """  
+  
+  def __init__(self, channel):
+    """ Constructor. 
+    
+    Args: 
+    channel: A grpc.Channel. 
+    """
+    
+    self.SayHello = channel.unary_unary(
+      "/models.Greeter/SayHello"
+      )
+    
+    self.SayManyHellos = channel.unary_stream(
+      "/models.Greeter/SayManyHellos"
+      )
+    
+
+class GreeterServicer(object):
+  """ Interface exported by the server. """  
+  
+  def SayHello(self, request, context):
+    context.set_code(grpc.StatusCode.UNIMPLEMENTED)
+    context.set_details('Method not implemented!')
+    raise NotImplementedError('Method not implemented!')
+  
+  
+  def SayManyHellos(self, request, context):
+    context.set_code(grpc.StatusCode.UNIMPLEMENTED)
+    context.set_details('Method not implemented!')
+    raise NotImplementedError('Method not implemented!')
+  
+  
+
+def add_GreeterServicer_to_server(servicer, server):
+  rpc_method_handlers = {
+    'SayHello': grpc.unary_unary_rpc_method_handler(
+      servicer.SayHello
+    ),
+    'SayManyHellos': grpc.unary_stream_rpc_method_handler(
+      servicer.SayManyHellos
+    ),
+  }
+  generic_handler = grpc.method_handlers_generic_handler(
+    'models.Greeter', rpc_method_handlers)
+  server.add_generic_rpc_handlers((generic_handler,))
+