make smithy-rs the source of truth for extra AWS model tests (#3686)

## Motivation and Context

There are extra service specific model tests in various
`aws/sdk/aws-models/[sdk-id]-tests.smithy` files. These are currently
manually duplicated to `aws-sdk-rust/aws-models`. This PR seeks to make
`smithy-rs` the single source of truth for these tests and remove the
need to copy them into `aws-sdk-rust` at all.

## Description

* move all `-tests.smithy` into a new sibling directory
`aws-models-extra` and _ALWAYS_ include these regardless of what the
path to `aws-models` is (e.g. even when overriding it and generating the
full SDK by setting `-Paws.sdk.models.path`
* move all `-tests.smithy` from `aws-sdk-rust/aws-models` into this
directory (previously only `s3`, `route53`, and `glacier` were in this
repo but there are also additional tests for `ebs`, `batch`, and `sqs`.
This makes `smithy-rs` the only source of truth for additional AWS SDK
model tests
    * see https://github.com/awslabs/aws-sdk-rust/pull/1161
* update the `s3` model to latest and revert
ttps://github.com/smithy-lang/smithy-rs/pull/3641

## Testing
Local + CI

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