debugger: rename internal library for clarity

When I moved these files from node-inspect to Node.js core, I put them
in lib/internal/inspector. That was a mistake. They should be in
lib/internal/debugger.

PR-URL: https://github.com/nodejs/node/pull/39080


Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>