[ci] Start moving podspec check to ARM (#6782)

Now that `google_maps_flutter` supports ARM simulators, we should be able to move this task to ARM. This adds the ARM version in bringup mode, with a new name to reflect the fact that it is doing more that just checking podspecs now.

Once this propagates and is green, the x64 version will be removed.

Part of flutter/flutter#141493

Author: stuartmorgan-g

.ci.yaml

@@ -975,6 +975,18 @@ targets:
           {"dependency": "swift_format", "version": "build_id:8797338980206841409"}
         ]
 
+  - name: Mac_arm64 macos_repo_checks
+    recipe: packages/packages
+    bringup: true # New target
+    timeout: 30
+    properties:
+      version_file: flutter_master.version
+      target_file: macos_repo_checks.yaml
+      dependencies: >
+        [
+          {"dependency": "swift_format", "version": "build_id:8797338980206841409"}
+        ]
+
   ### macOS desktop tasks ###
   # macos-platform_tests builds all the packages on ARM, so this build is run
   # on Intel to give us build coverage of both host types.