ci: upgrade to Xcode 16 (#2294)

Author: Saadnajmi

.ado/variables/vars.yml

@@ -1,6 +1,6 @@
 variables:
   VmImageApple: macos-latest-internal
-  xcode_friendly_name: 'Xcode 15.2'
-  xcode_version: '/Applications/Xcode_15.2.app'
-  ios_version: '17.2'
-  ios_simulator: 'iPhone 15'
+  xcode_friendly_name: 'Xcode 16.0'
+  xcode_version: '/Applications/Xcode_16.0.app'
+  ios_version: '18.0'
+  ios_simulator: 'iPhone 16'