Improve the messaging for unsupported (Canary) versions of IDEs

We should improve the messaging around IDE versions that we don't yet support. Generally this is Canary versions of Android Studio (https://github.com/flutter/flutter-intellij/issues/4136 and related for context).

We currently have a message that displays after you've opened a project. However, unless people have an existing project, they won't see this message.

cc @stevemessick