src,test: debug is now an alias for inspect

`node debug` is now an alias of `node inspect`. This is intended to be
a minimal change – it does not get rid of the the debugger code. That
can be done in a follow-on.

PR-URL: https://github.com/nodejs/node/pull/11441


Reviewed-By: bnoordhuis - Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: joshgav - Josh Gavant <josh.gavant@outlook.com>
Reviewed-By: cjihrig - Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: targos - Michaël Zasso <mic.besace@gmail.com>