4461 Fix bugs in Dart Implementation of the Pigeon API  (cla: yes, waiting for tree to go green, p: webview_flutter, platform-android)

4465 [path_provider] Federate mobile implementations (cla: yes, p: path_provider, platform-ios, platform-android)

4466 Remove -Werror from deprecated plugin Android builds (cla: yes, p: android_alarm_manager, p: android_intent, p: connectivity, platform-android)

4467 update build_runner dependencies in android_intent and file_selector example (cla: yes, p: android_intent, p: file_selector, platform-web)

4468 [ci] Remove unused dep from file_selector. (cla: yes, waiting for tree to go green, p: file_selector, platform-web)