[debugger] Add entire directory to files in .isolate

Previously, tests in the newly added test/debugger/debug directory were
not executed on CQ.

BUG=v8:5530

Review-Url: https://codereview.chromium.org/2484713002
Cr-Commit-Position: refs/heads/master@{#40819}

test/debugger/debugger.isolate

@@ -7,10 +7,7 @@
     ['v8_enable_inspector==1', {
       'variables': {
         'files': [
-          './debugger.status',
-          './protocol/',
-          './test-api.js',
-          './testcfg.py',
+          './',
         ],
       },
     }],