Change Flutter SDK from command line

I maintain [Puro](https://puro.dev/), a tool that manages Flutter versions and attempts to automatically configure VSCode and IntelliJ to point to the desired environment.

To accomplish this with IntelliJ the tool writes to `Dart_SDK.xml` and `Dart_Packages.xml`, filling in the dart SDK path and roots in a similar manner to the flutter-intellij plugin.

Unfortunately writing to these config files while IntelliJ is running causes the IDE to freak out and disable flutter support in the project or show a "The current configured Flutter SDK is not known to be fully supported" banner.

It would be nice if the configuration file was simpler (it seems pretty archaic) or we could run a command to switch the SDK.