Don't allow `test-util` feature in compile time dependencies (#2843)

During the orchestrator implementation, a bug was introduced that always
enabled the `test-util` feature on `aws-smithy-runtime` in the generated
crates. This led to several pieces of non-test code relying on test-only
code, specifically around `SystemTime` implementing `TimeSource`.

This PR fixes that issue, and also fixes another issue where the
`RuntimeComponentsBuilder` was being initialized without a name for the
service config.

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