Feature: Add smithy orchestrator (#2447)

* add: WIP for smithy orchestrator

* add: publish = false to the new, unreleased crates

* undo: more extraneous changes

* fix: correctly declare `publish = false`

* feature: add layered config bag

* Update aws/sdk/integration-tests/smithy_orchestrator/Cargo.toml

Co-authored-by: John DiSanti <jdisanti@amazon.com>

* add: READMEs to new crates
add: external-types.toml to new crates
add: LICENSEs to new crates
update: crate organization and naming
update: interceptor errors per RFC 22
update: token bucket errors per RFC 22

* fix: bad imports in integration test

* fix: error struct naming

* fix: err source issue

* fix: clippy lints
fix: TODOs with no subject

* fix: broken token bucket test
add: docs.rs metadata to cargo toml of new crates

* update: crate naming

* fix: broken test import

* fix: cargo doc issues

* update: aws-smithy-runtime external-types.toml

* remove: unused deps
fix: move allowed external types to correct crate

* add: exception for aws_smithy_types

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Co-authored-by: Russell Cohen <rcoh@amazon.com>
Co-authored-by: John DiSanti <jdisanti@amazon.com>