api: Sketch add_transport_from_qr(), add_transport(), list_transports(), delete_transport() APIs (#6589)

Four new APIs `add_transport_from_qr()`, `add_transport()`,
`list_transports()`, `delete_transport()`, as described in the draft at
"API".

The `add_tranport*()` APIs automatically stops and starts I/O; for
`configure()` the stopping and starting is done in the JsonRPC bindings,
which is not where things like this should be done I think, the bindings
should just translate the APIs.

This also completely disables AEAP for now.

I won't be available for a week, but if you want to merge this already,
feel free to just commit all review suggestions and squash-merge.

deltachat-rpc-client/tests/test_securejoin.py

@@ -463,6 +463,7 @@ def test_qr_new_group_unblocked(acfactory):
     assert ac2_msg.chat.get_basic_snapshot().is_contact_request
 
 
+@pytest.mark.skip(reason="AEAP is disabled for now")
 def test_aeap_flow_verified(acfactory):
     """Test that a new address is added to a contact when it changes its address."""
     ac1, ac2 = acfactory.get_online_accounts(2)