events: remove emit micro-optimizations

With improvements in V8, using separate emit functions is no longer
necessary and can instead be replaced by the spread operator.

improvement                             confidence        p.value
events/ee-emit.js n=2000000                 2.98 %        0.09852489
events/ee-emit-2-args.js n=2000000          4.19 %    *** 0.0001914216
events/ee-emit-6-args.js n=2000000         61.69 %    *** 6.611964e-35
events/ee-emit-diff-args.js n=2000000      -0.36 %        0.305069
events/ee-once.js n=20000000                6.42 %    *** 1.27831e-06

PR-URL: https://github.com/nodejs/node/pull/16869


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Bryan English <bryan@bryanenglish.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Benedikt Meurer <benedikt.meurer@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>