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