Shard & set hard timeout for telemetry_perf_unittests

testing/buildbot/chromium.android.json

 {
   "Android GN Builder (dbg)": {
     "additional_compile_targets": [
       "blimp_tests",
       "chrome_public_apk",
       "chrome_public_test_apk",
       "content_shell_apk",
       "content_shell_test_apk",
       "system_webview_apk"
     ]
@@ skipping 953 matching lines @@
           "telemetry_perf_unittests"
         ],
         "swarming": {
           "can_use_on_swarming_builders": true,
           "dimension_sets": [
             {
               "device_os": "KTU84P",
               "device_type": "hammerhead"
             }
           ],
-          "hard_timeout": 960
+          "hard_timeout": 960,
+          "shards": 12
         }
       }
     ]
   },
   "Jelly Bean Tester": {
     "gtest_tests": [
       {
         "test": "android_webview_unittests"
       },
       {
@@ skipping 855 matching lines @@
       },
       {
         "test": "chrome_sync_shell_test_apk"
       },
       {
         "test": "content_shell_test_apk"
       }
     ]
   }
 }