[native] Return only header for datasize request

[zation99]

Description

When responding data size request, a body can be returned with up to 1M of data. If there are a lot of sources, it can lead to large amount of mem use.
This patch makes it only return the header when requesting data size.
Note that this still calls getData() same as previously. An alternative approach is tested where we immediately return the target buffer bytes size without invoking getData(). While it works, it leads to more requests made from the consumers because its driver just keeps requesting it. So we still keep this approach.

Motivation and Context

Impact

Test Plan

Contributor checklist

• Please make sure your submission complies with our contributing guide, in particular code style and commit standards.
• PR description addresses the issue accurately and concisely. If the change is non-trivial, a GitHub Issue is referenced.
• Documented new properties (with its default value), SQL syntax, functions, or other functionality.
• If release notes are required, they follow the release notes guidelines.
• Adequate tests were added if applicable.
• CI passed.

Release Notes

Please follow release notes guidelines and fill in the release notes below.

== NO RELEASE NOTE ==


If release note is NOT required, use:

== NO RELEASE NOTE ==