tools: check-imports using utf-8

PR-URL: https://github.com/nodejs/node/pull/30220


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>