lib: remove _debugger.js

The file no longer works after the removal of the --debug/--debug-brk
switches in commit 47f8f74 ("src: remove support for --debug".)

This commit also removes several tests that still referenced the
old debugger but were either unit-testing its internals or passing
for the wrong reason (like expecting an operation to fail, which
it did because the debugger is gone.)

PR-URL: nodejs#12495
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/internal/bootstrap_node.js

@@ -122,9 +122,7 @@
 
         const internalModule = NativeModule.require('internal/module');
         internalModule.addBuiltinLibsToObject(global);
-        run(() => {
-          evalScript('[eval]');
-        });
+        evalScript('[eval]');
       } else if (process.argv[1]) {
         // make process.argv[1] into a full path
         const path = NativeModule.require('path');
@@ -143,7 +141,7 @@
         }
 
         preloadModules();
-        run(Module.runMain);
+        Module.runMain();
       } else {
         preloadModules();
         // If -i or --interactive were passed, or stdin is a TTY.
@@ -417,33 +415,6 @@
     }
   }
 
-  function isDebugBreak() {
-    return process.execArgv.some((arg) => /^--debug-brk(=[0-9]+)?$/.test(arg));
-  }
-
-  function run(entryFunction) {
-    if (process._debugWaitConnect && isDebugBreak()) {
-
-      // XXX Fix this terrible hack!
-      //
-      // Give the client program a few ticks to connect.
-      // Otherwise, there's a race condition where `node debug foo.js`
-      // will not be able to connect in time to catch the first
-      // breakpoint message on line 1.
-      //
-      // A better fix would be to somehow get a message from the
-      // V8 debug object about a connection, and runMain when
-      // that occurs.  --isaacs
-
-      const debugTimeout = +process.env.NODE_DEBUG_TIMEOUT || 50;
-      setTimeout(entryFunction, debugTimeout);
-
-    } else {
-      // Main entry point into most programs:
-      entryFunction();
-    }
-  }
-
   function checkScriptSyntax(source, filename) {
     const Module = NativeModule.require('module');
     const vm = NativeModule.require('vm');

node.gyp

@@ -23,7 +23,6 @@
     'library_files': [
       'lib/internal/bootstrap_node.js',
       'lib/_debug_agent.js',
-      'lib/_debugger.js',
       'lib/assert.js',
       'lib/buffer.js',
       'lib/child_process.js',