module: enable dynamic import flag for esmodules

currently if you want to use dynamic import you must use both the
`--experimental-modules` and the `--harmony-dynamic-imports` flags.
Chrome is currently shipping dynamic import unflagged, the flag
only remains in V8 to guard embedders who have not set the appropriate
callback from throwing an unhandled rejection when the feature is used.

As such it is reasonable to enable the flag by default for
`--experimental-modules`

PR-URL: https://github.com/nodejs/node/pull/18387


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Jan Krems <jan.krems@gmail.com>
Reviewed-By: Bradley Farias <bradley.meck@gmail.com>
Reviewed-By: Guy Bedford <guybedford@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>