Add support for Streaming Response Bodies (#338)

* Assert field-by-field equality in protocol tests

Protocol tests currently use `PartialEq`, but when we add streaming members, we can no longer compare equality synchronously & without
side effects. This diff removes `PartialEq` from output shapes (we may re add it later for non-streaming shapes) & instead asserts equality of each output member in turn.

* Cleaner version of body streaming, still some work to get it to work with tests

* Finalize protocol test support

* Add default to the operation parsers

* Add helper for isStreaming on member shapes

* Cleanups & add test

* allow upper case keys in rustTemplate