Add full Event Stream marshalling support and working S3 example (#667)

* Add generic error support to event stream unmarshallers

* Validate content-type in event stream unmarshaller

* Implement header marshalling and test

* Introduce SharedPropertyBag

* Send empty end frame

* Add `try_recv_initial()` to Receiver

* Set up Event Stream approval list and shrink default service list

* Add support and example for S3 SelectObjectContent

* Improve Event Stream error ergonomics

* Update changelog

* Fix CI

* Split generic error parsing in `Protocol`

* Incorporate CR feedback

* Make raw message available when failng to unmarshall into event or error