Fix the S3 alternate runtime retries test in orchestrator mode (#2825)

This PR fixes the S3 `alternative-async-runtime` retry tests. The retry
backoff time was being included in the operation attempt timeout, which
I think is undesirable as it makes retry config much harder to get right
since the backoff times are not predictable (they have randomness
incorporated into them). The overall operation timeout is the only one
that needs to incorporate backoff times.

In addition, this PR also:
- Updates READMEs for the `aws-smithy-runtime-api` and
`aws-smithy-runtime` crates
- Adds top-level crate docs to describe features to `aws-smithy-runtime`
- Copies `capture_test_logs` into `aws-smithy-runtime` so that it can be
used (just about) everywhere instead of just in `aws-config`
- Adds service/operation name to the tracing `invoke` span so it's
possible to tell which operation the events are for
- Makes the `Debug` impl for `Identity` useful
- Adds a ton of trace/debug spans and events to the orchestrator
- Fixes an issue in `aws-smithy-runtime` where a huge amount of the
orchestrator tests weren't being compiled due to a removed feature flag

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