WebRTC: Move iOS Simulator bots to client.webrtc + add trybots

scripts/slave/recipes/webrtc/standalone.expected/tryserver_webrtc_ios64_simulator.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/bot_update.py",
       "--master",
       "tryserver.webrtc",
       "--builder",
-      "ios_arm64_rel",
+      "ios64_simulator",
       "--slave",
       "slavename",
       "--spec",
       "cache_dir = None\nsolutions = [{'deps_file': 'DEPS', 'managed': True, 'name': 'src', 'url': 'https://chromium.googlesource.com/external/webrtc'}, {'deps_file': 'DEPS', 'managed': True, 'name': 'webrtc-limited', 'url': 'https://chrome-internal.googlesource.com/chrome/deps/webrtc-limited'}]\ntarget_os = ['ios', 'mac']",
       "--root",
       "src",
       "--revision_mapping_file",
       "{\"src\": \"got_revision\"}",
       "--issue",
       "666666",
@@ skipping 44 matching lines @@
   },
   {
     "cmd": [
       "python",
       "-u",
       "[DEPOT_TOOLS]/gclient.py",
       "runhooks"
     ],
     "env": {
       "GYP_CROSSCOMPILE": "1",
-      "GYP_DEFINES": "OS=ios build_with_libjingle=1 chromium_ios_signing=0 clang=1 component=static_library dcheck_always_on=1 fastbuild=1 gomadir='[BUILD]/goma' key_id='' mac_sdk=10.9 target_arch=arm64 use_goma=1",
+      "GYP_DEFINES": "OS=ios build_with_libjingle=1 chromium_ios_signing=0 clang=1 component=static_library dcheck_always_on=1 fastbuild=1 gomadir='[BUILD]/goma' key_id='' mac_sdk=10.9 target_arch=x64 use_goma=1",
       "GYP_GENERATORS": "ninja"
     },
     "name": "gclient runhooks"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/compile.py",
       "--target",
-      "Release-iphoneos",
+      "Debug-iphonesimulator",
       "--src-dir",
       "[SLAVE_BUILD]/src",
       "--build-tool",
       "ninja",
       "--compiler",
       "goma-clang",
       "--goma-dir",
       "[BUILD]/goma",
       "--",
       "All"
     ],
     "name": "compile"
   }
 ]