debugger: rename internal module

All other files in `lib/internal` do not start with `_`. For
consistency, move `lib/internal/debugger/_inspect.js` to
`lib/internal/debugger/inspect.js`.

PR-URL: https://github.com/nodejs/node/pull/39378


Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: James M Snell <jasnell@gmail.com>