Render smoke tests for services without support for account ID routing (#3808)

## Motivation and Context
Follow-up on https://github.com/smithy-lang/smithy-rs/pull/3799

## Description
This PR updates the smoke test rendering process for services whose
models specify the `smokeTests` trait
([example](https://github.com/awslabs/aws-sdk-rust/blob/c349073b345a576d18ab7729afc7b75ae273d2ac/aws-models/sns.json#L3392-L3404)).
Previously, `SmokeTestsDecorator` skipped rendering when
`useAccountIdRouting` was set to true in the vendor parameters, which is
the default for `AwsVendorParams`. Even though the Rust SDK does not
currently support the account ID routing, it is safe to render these
tests. This is because existing smoke tests do not rely on this feature,
and when account ID routing is used, the Rust SDK will fall back to
other means to sourcing the identity.

This PR includes a minor fix: it uses `aws_config` to load default
configurations. `config::Builder::new()` would have no credentials
provider chain available, which would then result in test failures at
runtime.
```
---- test_list_certificates_success stdout ----
thread 'test_list_certificates_success' panicked at sdk/acm/tests/smoketests.rs:22:9:
request should succeed: DispatchFailure(DispatchFailure { source: ConnectorError { kind: Other(None), source: NoMatchingAuthSchemeError(ExploredList { items: [ExploredAuthOption { scheme_id: AuthSchemeId { scheme_id: "sigv4" }, result: NoIdentityResolver }], truncated: false }), connection: Unknown } })
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
```

By bringing `aws-config`, the `SmokeTestsDecoratorTest` no longer works,
since the AWS runtime crates required by `aws-config` conflict with
those generated by `awsSdkIntegrationTest` (a known limitation). For
example:
```
error: package collision in the lockfile: packages aws-credential-types v1.2.0 (smithy-rs/aws/rust-runtime/aws-credential-types) and aws-credential-types v1.2.0 (smithy-rs/aws/sdk/build/aws-sdk/sdk/aws-credential-types) are different, but only one can be written to lockfile unambiguously
```
Therefore, we removed `SmokeTestsDecoratorTest.kt` _only_ in this PR to
ship the feature, but are planning to restore it in the next PR by
directly testing `SmokeTestsInstantiator` without using
`awsSdkIntegrationTest`.

## Testing
- [x] Existing tests in CI
- [x] Executed and passed smoke tests for services that support them in
our release pipeline

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