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: #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>

Author: Trott

lib/internal/debugger/_inspect.js renamed to lib/internal/debugger/inspect.js

@@ -18,5 +18,5 @@ markBootstrapComplete();
 
 // Start the debugger agent.
 process.nextTick(() => {
-  require('internal/debugger/_inspect').start();
+  require('internal/debugger/inspect').start();
 });