http2: refer to stream errors by name

Display the constant name instead of a stream error code
in the error message, because the numerical codes give absolutely
no clue about what happened when an error is emitted.

PR-URL: https://github.com/nodejs/node/pull/18966


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Minwoo Jung <minwoo@nodesource.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>