Move Scribe tests to extensions and attach oncall (6 / n)

Summary: Moves scribe tests  from `hphp/facebook/test/ext/` to `hphp/facebook/extensions/scribe/test/`. This will help decouple tests such that the extension team can own the tests.

Differential Revision: D67226077

fbshipit-source-id: b48b35198a16c1a9e913fe11f2305fdc07e14de1

hphp/test/run.php

@@ -563,6 +563,7 @@ function find_test_files(string $file): vec<string>{
     'thrift' => 'hphp/facebook/extensions/thrift/test',
     'flighttracker' => 'hphp/facebook/extensions/flighttracker/test',
     'fci' => 'hphp/facebook/extensions/fci/test',
+    'scribe' => 'hphp/facebook/extensions/scribe/test',
   ];
 
   $pattern = $mappage[$file] ?? null;