Fix request compression

[Velfi]

Description

This PR includes several fixes for request compression:

• aws_smithy_compression::body::compress::CompressedBody will no longer incorrectly return the inner body's SizeHint, returning SizeHint::default() instead.
• Fixed a bug where compressed payloads would have an incorrect content length, causing those requests to hang.
• Compress in-memory request payloads instead of the previous lazy approach.

Testing

Tests are included. Additionally, I ran a reproducer for a user issues to ensure that their use case works:

#[tokio::test]
async fn use_case_reproducer() {
    tracing_subscriber::fmt::init();
    let shared_config = aws_config::from_env()
        .region(aws_sdk_cloudwatch::config::Region::new("us-west-2"))
        .load()
        .await;
    let service_config = aws_sdk_cloudwatch::config::Config::from(&shared_config)
        .to_builder()
        .request_min_compression_size_bytes(1)
        .build();
    let client = Client::from_conf(service_config);

    tracing::info!("sending metrics...");
    client
        .put_metric_data()
        .namespace("CloudWatchTestMetricsBrivinc")
        .metric_data(
            aws_sdk_cloudwatch::types::MetricDatum::builder()
                .metric_name(format!("MyMetricNameIsALittleLong"))
                .value(0.0)
                .build(),
        )
        .send()
        .await
        .unwrap();
}

---

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[github-actions]

A new generated diff is ready to view.

• AWS SDK (ignoring whitespace)
• Client Test (ignoring whitespace)
• No codegen difference in the Server Test
• No codegen difference in the Server Test Python
• No codegen difference in the Server Test Typescript

A new doc preview is ready to view.

[github-actions]

A new generated diff is ready to view.

• AWS SDK (ignoring whitespace)
• Client Test (ignoring whitespace)
• No codegen difference in the Server Test
• No codegen difference in the Server Test Python
• No codegen difference in the Server Test Typescript

A new doc preview is ready to view.

[github-actions]

A new generated diff is ready to view.

• AWS SDK (ignoring whitespace)
• Client Test (ignoring whitespace)
• No codegen difference in the Server Test
• Server Test Python (ignoring whitespace)
• No codegen difference in the Server Test Typescript

A new doc preview is ready to view.

[ysaito1001]

Left minor comments, but LGTM!

[github-actions]

A new generated diff is ready to view.

• AWS SDK (ignoring whitespace)
• Client Test (ignoring whitespace)
• No codegen difference in the Server Test
• Server Test Python (ignoring whitespace)
• No codegen difference in the Server Test Typescript

A new doc preview is ready to view.

[aajtodd]

Fix and ship (Yuki's callout).

[github-actions]

A new generated diff is ready to view.

• AWS SDK (ignoring whitespace)
• Client Test (ignoring whitespace)
• No codegen difference in the Server Test
• Server Test Python (ignoring whitespace)
• No codegen difference in the Server Test Typescript

A new doc preview is ready to view.