Add support for request bodies on DELETE reuqests

I'm working on a DuckDB Catalog Extension where the underlying API supports bulk-delete only via sending a request body in a DELETE request.
Without a request body, I have two options:
- issue a per-row DELETE request
- use a custom HTTP Client instead of re-using HTTPUtil from DuckDB

Start by locating HTTPUtil and the HTTP client entry point used for DELETE requests. Trace how request methods and bodies are passed, then verify that a DELETE request can carry a body without breaking existing requests; done means the bulk-delete API described in the issue can be reused through HTTPUtil.

Written by the indexing model from the issue text.