src: turn `GET_OFFSET()` into an inline function

There’s no need for this to be a macro.

PR-URL: https://github.com/nodejs/node/pull/29357


Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Masashi Hirano <shisama07@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>