Fix `canary-wasm` not being able to locate generated crates (#3472)

## Motivation and Context
Fixes the issue of `canary-wasm` not being able to locate generated
crates in our release pipeline

## Description
The `canary-wasm` crate has
[Cargo.toml](https://github.com/smithy-lang/smithy-rs/blob/main/tools/ci-cdk/canary-wasm/Cargo.toml)
checked-in, whose SDK dependencies assume path locations with respect to
build artifacts within the `smithy-rs` repository. However, those
locations can be different in our release pipeline (the same reason why
there's no manifest file checked-in for
[canary-lambda](https://github.com/smithy-lang/smithy-rs/tree/main/tools/ci-cdk/canary-lambda)
and it needs to be generated on the fly by `canary-runner`'s
`build-bundle` subcommand).

To fix this, `canary-runner` now generates the manifest for
`canary-wasm`.

## Testing
- [x] Added unit tests for `canary-runner`
- [x] Verified in our release pipeline that canary built and passed

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