[various] Update min macOS versions (#3987)

- Updates all macOS plugins to 10.14 as a minimum version, matching Flutter `stable`.
- Checks in the results of building all macOS examples with stable to bring them up to current with auto-migrations (and in some cases, with having ever been built, in the case of some examples with plugins where the CocoaPods changes were never committed).

All Runner.xcodeproj and Runner.xcworkspace changes are 100% tool-generated.

Also updates the repo tooling to know about a few more build-only example files that should not be flagged as potentially interesting for changelogs.

script/tool/test/common/package_state_utils_test.dart

@@ -78,8 +78,11 @@ void main() {
         'packages/a_plugin/example/android/build.gradle',
         'packages/a_plugin/example/android/gradle/wrapper/gradle-wrapper.properties',
         'packages/a_plugin/example/ios/Runner.xcodeproj/project.pbxproj',
+        'packages/a_plugin/example/ios/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme',
         'packages/a_plugin/example/linux/flutter/CMakeLists.txt',
+        'packages/a_plugin/example/macos/Podfile',
         'packages/a_plugin/example/macos/Runner.xcodeproj/project.pbxproj',
+        'packages/a_plugin/example/macos/Runner.xcworkspace/contents.xcworkspacedata',
         'packages/a_plugin/example/windows/CMakeLists.txt',
         'packages/a_plugin/example/pubspec.yaml',
         // Pigeon platform tests, which have an unusual structure.