Only generate the presign customize operation method for ops that support it

[Velfi]

THIS IS A BREAKING CHANGE, DO NOT MERGE

Exactly what it says on the tin.

What it currently generates

impl<E, B> CustomizableOperation<crate::operation::put_object::PutObject, E, B> {
    /// Sends the request and returns the response.
    #[allow(unused_mut)]
    pub async fn presigned(
        mut self,
        presigning_config: crate::presigning::PresigningConfig,
    ) -> ::std::result::Result<crate::presigning::PresignedRequest, crate::error::SdkError<E>>
    where
        E: std::error::Error + ::std::marker::Send + ::std::marker::Sync + 'static,
        B: crate::client::customize::internal::CustomizablePresigned<E>,
    {
        self.execute(move |sender, conf| sender.presign(conf, presigning_config)).await
    }
}

Problems with this approach

• Will create an impl for each operation that needs one. If all operations need to define a customizable operation impl, then that's potentially a lot of redundant code.
• We've been generating the presign method for all S3 ops, even though it's only guaranteed to work for a subset. Before merging this, we'll probably want to undo the changes to presigning while keeping the underlying new way of defining customizable op impls.

What I need from you

• Does this codegen approach look sound?
• Should we be doing this for things other than presigning?
• How should we decide when to do impls per-operation vs for all operations at once?

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.

[ysaito1001]

Thanks for the PR. This gives us a good starting point for discussion.

We've been generating the presign method for all S3 ops, even though it's only guaranteed to work for a subset. Before merging this, we'll probably want to undo the changes to presigning while keeping the underlying new way of defining customizable op impls.

Talked about this briefly offline, and it might be better to keep the presign method for all operations so we don’t break things for people. There's also an issue (linked off from this TODO) that says All S3 requests should be presignable—this is the behavior of the Ruby SDK. so that's something to keep in mind.