Consider low-hanging fruit for reducing usage reporting memory usage

[glasser]

• Drop reference to original protobuf once encoded
• Drop reference to encoded protobuf once compressed
• Maybe use streaming to drop reference to compressed body once sent
• Make it easier to set timeouts for the fetch? Might be a challenge because abortcontroller isn't necessarily supported by all potential Fetcher implementations. But we could at the very least publish eg @apollo/utils.nodeFetchWithTimeout that wraps node-fetch with a timeout. (edit: oh actually we assume signal support in Fetcher so we can just provide it as an option if we really want)