Make change testable

[in_app_purchase] Update app-facing package to new analysis options (f…

…lutter#4969)

[google_maps_flutter] Switch app-facing package to new analysis optio…

…ns (flutter#4716)

[in_app_purchase] Update Android to new analysis options (flutter#4937)

[url_launcher] Fixed missing # in links href when opening in new tab …

…on the web (flutter#4221)

[image_picker] Support reading WebP images for iOS (flutter#4448)

[webview] Fix comments (accidentially mixed `//` with `///`) (flutter…

…#4907)

[video_player] Update app-facing package analysis options (flutter#4786)

[path_provider] Switch iOS to an internal method channel (flutter#4921)

[path_provider] Use a different Android channel name (flutter#4912)