Circle CI: Use new generation machines in macOS jobs

Summary:
Use Circle CI's new generation macOS resource class in all iOS and macOS jobs. This resource provides additional resources and should reduce execution time in our iOS and macOS jobs by about 40-50%.

Changelog: [Internal]

Reviewed By: cortinico

Differential Revision: D35294738

fbshipit-source-id: 817a8f80e774a11d23d9466d938064ac41625256

.circleci/config.yml

@@ -80,6 +80,7 @@ executors:
     <<: *defaults
     macos:
       xcode: &_XCODE_VERSION "13.0.0"
+    resource_class: macos.x86.medium.gen2
 
 # -------------------------
 #        COMMANDS
@@ -888,8 +889,7 @@ jobs:
             - hermesc/linux
 
   build-hermesc-macos:
-    macos:
-      xcode: &_XCODE_VERSION "13.0.0"
+    executor: reactnativeios
     working_directory: ~/hermes
     environment:
       - HERMES_WS_DIR: *hermes_workspace_root