The new file_selector plugin has essentially the same functionality as FDE's file_chooser plugin, but the method channel API is slightly different. This tracks migrating file_chooser over to become file_selector implementations for desktop (at which point file_chooser will be removed).

• Windows
• macOS
• Linux

This is the first instance of a plugin with native desktop UI, so we don't currently have a good testing story. We should start with at least getting PRs for moving the implementation over and adding examples, and then we can evaluate how to move forward. (My preference would be to file a follow-up for integration tests, since I think that's going to be a substantial project, and having it be a standard, published plugin that also supports web and mobile is a significant improvement over maintaining file_chooser even without solving the pre-existing testing problem.)