Add isolate.clean_isolated_files and use in all related recipes.

scripts/slave/recipes/gpu/build_and_test.expected/linux_release_tryserver.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/cleanup_temp.py"
     ],
     "name": "cleanup temp"
   },
   {
@@ skipping 71 matching lines @@
     ],
     "env": {
       "GYP_DEFINES": "archive_gpu_tests=1 blink_logging_always_on=1 component=static_library dcheck_always_on=1 disable_glibcxx_debug=1 gomadir='[BUILD]/goma' internal_gles2_conform_tests=1 target_arch=x64 test_isolation_mode=archive test_isolation_outdir=https://isolateserver.appspot.com use_goma=1"
     },
     "name": "gclient runhooks"
   },
   {
     "cmd": [
       "python",
       "-u",
+      "[BUILD]/scripts/slave/recipe_modules/isolate/resources/find_isolated_tests.py",
+      "--build-dir",
+      "[SLAVE_BUILD]/src/out/Release",
+      "--clean-isolated-files"
+    ],
+    "name": "clean isolated files"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
       "[BUILD]/scripts/slave/compile.py",
       "--target",
       "Release",
       "--src-dir",
       "[SLAVE_BUILD]/src",
       "--build-tool",
       "ninja",
       "--compiler",
       "goma",
       "--goma-dir",
@@ skipping 595 matching lines @@
       "[SLAVE_BUILD]/src/tools/swarming_client/run_isolated.py",
       "-H",
       "[dummy hash for gpu_unittests]",
       "-I",
       "https://isolateserver.appspot.com",
       "--"
     ],
     "name": "gpu_unittests"
   }
 ]