net: convert many Close tests to use parallel subtests

Also set a deadline in TestCloseWrite so that we can more easily
determine which kind of connection is getting stuck on the
darwin-arm64-corellium builder (#34837).

Change-Id: I8ccacbf436e8e493fb2298a79b17e0af8fc6eb81
Reviewed-on: https://go-review.googlesource.com/c/go/+/227588


Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>