[file_selector] Allow empty type groups (flutter#3261)

This was restricted under the assumption that there was no reason for an empty group to exist, but that's not actually true; on platforms with selectable groups in the native UI, it may be useful to provide specific options as well as a fallback option (e.g., "Text files" and "All files").

[file_selector] Allow empty type groups (flutter#3261)

This was restricted under the assumption that there was no reason for an empty group to exist, but that's not actually true; on platforms with selectable groups in the native UI, it may be useful to provide specific options as well as a fallback option (e.g., "Text files" and "All files").

[webview_flutter] update documentation to indicate gesture handling i…

…ssues on iOS 13.4 and 13.5 (flutter#3259)

[image_picker] Set up XCUITests (flutter#3254)

[device_info] Bump SDK

[device_info] Bump SDK

[device_info] Bump SDK

[device_info] Bump SDK

[device_info] Bump SDK

[device_info] Bump SDK