http2: make HTTP2ServerResponse more streams compliant

HTTP2ServerResponse.write would behave differently than
both http1 and streams. This PR makes it more compliant
with stream.Writable behaviour.

PR-URL: https://github.com/nodejs/node/pull/30964
Refs: https://github.com/nodejs/node/issues/29529


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>