lib: fix event race condition with -e

Commit c5b07d4e ("lib: fix beforeExit not working with -e") runs the
to-be-evaluated code at a later time than before because it switches
from `process.nextTick()` to `setImmediate()`.

It affects `-e 'process.on("message", ...)'` because there is now a
larger time gap between startup and attaching the event listener,
increasing the chances of missing early messages.  I'm reasonably
sure `process.nextTick()` was also susceptible to that, only less
pronounced.

Avoid the problem altogether by evaluating the code synchronously.
Harmonizes the logic with `Module.runMain()` from lib/module.js
which also calls `process._tickCallback()` afterwards.

PR-URL: https://github.com/nodejs/node/pull/11958


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>