[camera] Add `camera_platform_interface` package (flutter#3253)

* Make sure only camera_platform_interface has updates

* add dev dependency to async package

* refactored import to package import

* Fix formatting issues

[camera] Support Android 30 (flutter#3299)

[video_player] Fix mistake

[file_selector_platform_interface] Migrate to cross_file package (flu…

…tter#3286)

[file_selector] Initial implementation (flutter#3140)

Co-authored-by: Jason Panelli <[email protected]>

Revert "WIP"

This reverts commit 70e2adc.

[google_maps_flutter_web] Render custom Marker icons. (flutter#3273)

* Render markers fromBytes. Ensure initial icon is also preserved. Add test.
* Opt-out tests from null-safety until plugin is migrated.

[cross_file] An abstraction to allow working with files across multip…

…le platforms. (flutter#3260)

* Initial version of x_file package

* Renamed from x_file to cross_file

* Add back x_file type to file_selector

* Fix formatting issues

* Update homepage and version

* Added README.md

* Added missing copyright

* Revert "Added missing copyright"

This reverts commit cf7e8d5.

* Add missing copyright

Co-Authored-By: Jason Panelli <[email protected]>

* Renamed class implementation back to XFile

* Fix formatting issues

* Rename to cross_file

* Added code owners for cross_file package

Co-authored-by: Jason Panelli <[email protected]>

[google_maps_flutter_platform_interface] Add BitmapDescriptor.fromJso…

…n constructor. (flutter#3263)

This is required so serialized descriptors can be synchronously re-hydrated in the Web implementation. This will be removed/deprecated once the buildWidget API gets refactored.

[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").