src: move SIGINT watchdog utils to the contextify binding

These are used when evaluating scripts so it makes more sense
to put them in the contextify binding whose other methods are
going to be used together.

PR-URL: https://github.com/nodejs/node/pull/27290


Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>