test: update test-debugger-breakpoint-exists.js to use async/await

PR-URL: #44682
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

test/sequential/test-debugger-breakpoint-exists.js

@@ -8,20 +8,17 @@ const fixtures = require('../common/fixtures');
 const startCLI = require('../common/debugger');
 
 // Test for "Breakpoint at specified location already exists" error.
-{
-  const script = fixtures.path('debugger', 'three-lines.js');
-  const cli = startCLI([script]);
+const script = fixtures.path('debugger', 'three-lines.js');
+const cli = startCLI([script]);
 
-  function onFatal(error) {
-    cli.quit();
-    throw error;
+(async () => {
+  try {
+    await cli.waitForInitialBreak();
+    await cli.waitForPrompt();
+    await cli.command('setBreakpoint(1)');
+    await cli.command('setBreakpoint(1)');
+    await cli.waitFor(/Breakpoint at specified location already exists/);
+  } finally {
+    await cli.quit();
   }
-
-  cli.waitForInitialBreak()
-    .then(() => cli.waitForPrompt())
-    .then(() => cli.command('setBreakpoint(1)'))
-    .then(() => cli.command('setBreakpoint(1)'))
-    .then(() => cli.waitFor(/Breakpoint at specified location already exists/))
-    .then(() => cli.quit())
-    .then(null, onFatal);
-}
+})().then(common.mustCall());