2217 [url_launcher] Add url_launcher_platform_interface package (cla: yes)

2218 [package_info]remove AndroidX constraint (cla: yes)

2219 [camera]remove androidx constraint (cla: yes)

2220 [url_launcher]remove AndroidX constraint (cla: yes)

2221 [android_intent]remove AndroidX constraint (cla: yes)

2222 Fix testing instructions in CONTRIBUTING.md (cla: yes)

2223 [flutter_plugin_android_lifecycle] register the e2e plugin in the example app (cla: yes)

2226 [video_player] Add v2 embedding support (cla: yes)

2228 [url_launcher] Use url_launcher_platform_interface to handle calls (cla: yes)