repl: force editorMode in .load

The `.load` command would fail with any file that contains
multiline `.` operator expressions. This was particularly
noticeable when chaining promises or multi-line arrow
expressions.

This change Forces the REPL to be in `editorMode` while loading
a file from disk using the `.load` command.

Fixes: https://github.com/nodejs/node/issues/14022

PR-URL: https://github.com/nodejs/node/pull/14861


Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Refael Ackermann <refack@gmail.com>