Migrate from interop pods to source_files header access (#5760)

FirebaseABTesting.podspec

@@ -29,7 +29,11 @@ Firebase Cloud Messaging and Firebase Remote Config in your app.
   s.prefix_header_file = false
 
   base_dir = "FirebaseABTesting/Sources/"
-  s.source_files = base_dir + '**/*.[mh]'
+  s.source_files = [
+    base_dir + '**/*.[mh]',
+   'Interop/Analytics/Public/*.h',
+   'FirebaseCore/Sources/Private/*.h',
+  ]
   s.requires_arc = base_dir + '*.m'
   s.public_header_files = base_dir + 'Public/*.h', base_dir + 'Protos/developers/mobile/abt/proto/*.h'
   s.private_header_files = base_dir + 'Protos/developers/mobile/abt/proto/*.h'
@@ -40,7 +44,6 @@ Firebase Cloud Messaging and Firebase Remote Config in your app.
       'FIRABTesting_VERSION=' + String(s.version),
     'HEADER_SEARCH_PATHS' => '"${PODS_TARGET_SRCROOT}"'
   }
-  s.dependency 'FirebaseAnalyticsInterop', '~> 1.3'
   s.dependency 'FirebaseCore', '~> 6.8'
   s.dependency 'Protobuf', '~> 3.9', '>= 3.9.2'