Add standard acknowledgement to channels and apply usage in ibc transfer (#7263)

* gen ack proto type

* remove transfer ack

* change ics20 ack to use standard type

* update commented tests

* small typo fix

* revert back to module cdc

* update docs

* fix lint

* nit

* update ack event emission

* Update x/ibc-transfer/spec/01_concepts.md

* add comment for onacknowledgement

* Update proto/ibc/channel/channel.proto

Co-authored-by: Federico Kunze <31522760+fedekunze@users.noreply.github.com>
Co-authored-by: Christopher Goes <cwgoes@pluranimity.org>

docs/ibc/custom.md

@@ -340,7 +340,9 @@ receive acknowledegments with the IBC modules as byte strings.
 
 Thus, modules must agree on how to encode/decode acknowledgements. The process of creating an
 acknowledgement struct along with encoding and decoding it, is very similar to the packet data
-example above.
+example above. [ICS 04](https://github.com/cosmos/ics/tree/master/spec/ics-004-channel-and-packet-semantics#acknowledgement-envelope)
+specifies a recommended format for acknowledgements. This acknowledgement type can be imported from
+[channel types](https://github.com/cosmos/cosmos-sdk/tree/master/x/ibc/04-channel/types).
 
 #### Acknowledging Packets