Convenience methods to consume response body

[sagebind]

It would be nice to provide convenience methods for consuming a response body without storing it. This is a useful feature because if the user drops the response without reading the response body fully, the underlying connection cannot be reused and must be closed prematurely. While totally acceptable, this is not a good way to maintain high throughput since it prevents connection reuse.

The API could be something as simple as:

impl Body {
    pub fn consume(&mut self) -> io::Result<u64> {
        // ...
    }

    pub async fn consume_async(&mut self) -> io::Result<u64> {
        // ...
    }
}

Which would be essentially a convenience around io::copy(&mut response.body_mut(), &mut io::sink()).