Support PutMultipartOptions for MultipartStore::create_multipart for AWS/GCP.

[BearMinimum98]

Which issue does this PR close?

Adds PutMultipartOptions support to the low-level MultipartStore create flow via a new create_multipart_opts method.

This is implemented for AWS, GCP, in-memory, and wrapper stores. Azure returns NotSupported for non-default tags/attributes because Azure applies these options when finalizing block uploads, not when creating them. Supporting this in the low-level API would require local upload state, which could leak if uploads are never completed or aborted.

Closes #745

Rationale for this change

See issue.

What changes are included in this PR?

• Adds MultipartStore::create_multipart_opts
• For AWS/GCP, passes options through to the backend client
• For PrefixStore/ThrottledStore, delegates options to the wrapped multipart store
• For in-memory, stores attributes in PartStorage until completion
• For Azure, returns NotSupported for non-default tags/attributes

Are there any user-facing changes?

Yes. MultipartStore has a new default method, create_multipart_opts, so existing implementations remain source-compatible.

There are no breaking changes to the public API; the new method has a default implementation.

[BearMinimum98]

@alamb Would greatly appreciate a review today to be able to make it into the release tomorrow, if not possible, disregard. If it doesn't cut the release tomorrow, about when will the next minor version release be?

[alamb]

Thank you @BearMinimum98 -- this change makes sense to me and I found the PR well documented and well tested

🙏

[alamb]

👍

[alamb]

This makes sense to me as create_multipart is simply passing in PutMultipartOptions::default() -- adding the options explicitly makes sense

    async fn create_multipart(&self, path: &Path) -> Result<MultipartId> {
        self.client
            .multipart_initiate(path, PutMultipartOptions::default())
            .await
    }