Investigate the default http connector

[rcoh]

Currently the default http connector is Prebuilt: https://github.com/awslabs/smithy-rs/blob/bb5bbeb5cff2afb4b3664e95f5c63cae3a524379/aws/rust-runtime/aws-config/src/lib.rs#L463-L466

This means that timeout settings at a service level will be ignored. This should probably be ConnectorFn but the implications need to be considered.

[ysaito1001]

Fix released in https://github.com/awslabs/aws-sdk-rust/releases/tag/release-2023-03-30.