2712 [image_picker] Move core plugin to its own subdir. (cla: yes)

2713 [image_picker_platform_interface] Create image_picker_platform_interface package. (cla: yes)

2715 [connectivity_platform_interface] Remove Platform asserts. (cla: yes)

2716 [url_launcher] Remove an ephemeral file from macOS example (cla: yes)

2717 Add support for running Linux desktop tests on CI (cla: yes)

2718 [image_picker] Port core plugin to platform_interface APIs. (cla: yes)

2723 [battery] Bump to 1.0.0 (cla: yes)

2727 [url_launcher_web] Refactor unit tests to reduce flakiness. (cla: yes)