Split CDK app between `smithy-rs` and `aws-sdk-rust` (#3514)

## Motivation and Context
A prerequisite for running canary in smithy-rs CI

## Description
This PR is essentially refactoring so that `canary-stack.ts` library can
be used by both `smithy-rs` and `aws-sdk-rust`. CDK apps are then split
into `bin/smithy-rs` and `bin/aws-sdk-rust`; the former is used by our
local development and the latter is used by our internal release
pipeline.

Merging this PR to the main branch will not affect anything. However, we
will need to update our internal release pipeline to use
`bin/aws-sdk-rust/*` instead when we release new SDKs:
- `npm run build` -> `npx tsc && npx cdk --app "node
build/bin/aws-sdk-rust/canary.js" synth`
- `npx cdk bootstrap` -> `npx cdk bootstrap --app "ts-node
--prefer-ts-exts bin/aws-sdk-rust/canary.ts"`
- `npx cdk --app "node build/bin/canary-only.js" synth` -> `npx cdk
--app "node build/bin/aws-sdk-rust/canary-only.js" synth`
- `npx cdk --app "node build/bin/canary-only.js" deploy --outputs-file
cdk-outputs.json` -> `npx cdk --app "node
build/bin/aws-sdk-rust/canary-only.js" deploy --outputs-file
cdk-outputs.json`

Also, when this PR is merged, we're ready to deploy a new canary stack
`smithy-rs-canary-stack` used by smithy-rs CI.

## Testing
> we will need to update our internal release pipeline to use
`bin/aws-sdk-rust/*` instead

Verified internally that it passed the release pipeline.

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