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/README.md

@@ -1,5 +1,33 @@
 ## Languages known issues
 
+### Python
+
+- Assert the type required in your server/client since python is able to receive `Bytes array` or `utf8 strings`.
+
+```python
+def SayHello(self, request, context):
+    # request might be a byte array or a utf8 string
+
+    r = HelloRequest.HelloRequest().GetRootAs(request, 0)
+    reply = "Unknown"
+    if r.Name():
+        reply = r.Name()
+    # Issues might happen if type checking isnt present.
+    # thus encoding it as a `reply.decode('UTF-8')`
+    return build_reply("welcome " + reply.decode('UTF-8'))
+
+```
+
+This can be prevented by making sure all the requests coming to/from python are `Bytes array`
+
+```python
+def say_hello(stub, builder):
+    hello_request = bytes(builder.Output())
+    reply = stub.SayHello(hello_request)
+    r = HelloReply.HelloReply.GetRootAs(reply)
+    print(r.Message())
+```
+
 ### Go
 
 - Always requires the `content-type` of the payload to be set to `application/grpc+flatbuffers`