For some protocols, error type flag exists in error response body,
then we need to collect response stream to JS object and parse the
error type; For other protocols, error type flag doesn't exist in
error response body, then we don't need to collect the response
stream in error dispatcher. Instead, we can treat the error like
normal response. So that error shape supports the same traits as
normal responses like streaming, payload etc.

This is done by add a new flag in Protocol generator--
isErrorCodeInBody. When it return true, it means error type flag
exists in error response body, then body is parsed in errors
dispatcher, and each error deser only need to deal with parsed
response body in JS object format. When it returns false, it means
error type can be inferred without touching response body, then
error deser can access the error response intact.