Move protocol support out of aws-sdk-go-v2 into smithy-go

[lucix-aws]

The "AWS" HTTP protocols are entirely generic and should be supported natively. Client codegen via smithy-go is effectively unusable at this time.

[EDIT 8/20/25] The current plan is to not blindly port the protocol generators, but to rather totally rewrite (de)serialization in a way that pushes that support mostly into the runtime.

See #354.

[lucix-aws]

Requires completion of #505 as well.

[marsheth]

Hey, any update?