Add commands for easier running in Release mode

[peekpt]

It would be nice to have by default this Flutter modes in launch.json:
Run,
Profile
Debug
Release

and in the main file: Run | Debug | Profile | Release

Maybe also add something for building all the modes like: flutter build --split-per-abi

Build (apk)
Build (apk splitted)
Build (release)
Build (iOS)
Build (web)
Build (Win)
...

[DanTup]

These values come from the launch.json so we can't directly contribute them here. We could change the defaults/snippets that go into launch.json. It probably doesn't make sense to have Run/Debug in there, as that's controlled by whether you use Run -> Debug or Run -> Run Without Debugging (or use F5/Ctrl+F5). Adding an option to run Release builds may make sense though.

Maybe also add something for building all the modes like: flutter build --split-per-abi

I don't think build makes sense here, as this is for launching a debug session. Build already exists under the Run Build Task command, although we probably don't have all of these variations.