test: update and harden http2-reset-flood

* use new maxSessionInvalidFrames to lower the needed frames
* slow down requests to generate less redundant after-session-close
  requests

PR-URL: https://github.com/nodejs/node/pull/30534
Fixes: https://github.com/nodejs/node/issues/30505


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>