RFC: Smithy Orchestrator (#2439)

* add: WIP for smithy orchestrator RFC

* update: incorporate runtime plugin ideas

* update: RFC to reflect current impl of orchestrator
add: section on encapsulation

* update: RFC code examples

* update: changes section:
update: FAQ
update: set status to "implemented"

* fix: code example indentation

* no really, fix the indents

* I keep seeing more...

* Thanks Yuki

design/src/SUMMARY.md

@@ -56,6 +56,7 @@
   - [RFC-0031: Providing Fallback Credentials on Timeout](./rfcs/rfc0031_providing_fallback_credentials_on_timeout.md)
   - [RFC-0032: Better Constraint Violations](./rfcs/rfc0032_better_constraint_violations.md)
   - [RFC-0033: Improving access to request IDs in SDK clients](./rfcs/rfc0033_improve_sdk_request_id_access.md)
+  - [RFC-0034: Smithy Orchestrator](./rfcs/rfc0034_smithy_orchestrator.md)
 
 - [Contributing](./contributing/overview.md)
   - [Writing and debugging a low-level feature that relies on HTTP](./contributing/writing_and_debugging_a_low-level_feature_that_relies_on_HTTP.md)