Investigate body { type: "stream" } not tee'ing the stream

[kitsonk]

As discussed in #491 when requesting a body type of "stream", memory takes a thrashing because the body stream is .tee()ed. Should investigate just passing the body stream back, allowing it to be locked, as I am not sure there is any real benefit in tee'ing it, because we don't do that when the body is a "reader" for example, we just lock the stream.

[bodograumann]

Just saw this issue :-). It is resolved in oak 13 and later, but see also #642 as a follow-up.