Be able to define environment variables for Flutter test configuration

[michaelferwer]

Hello,

I open this ticket to add the functionality to define environment variables in flutter test configurations.
For example on my project, we use a private repository to store our flutter librairies.
We have to define a username, a token and the PUB_HOSTED_URL environment variable to be able to fetch those librairies.

It could be great if we could define those environment variables in configuration like Flutter configuration to run a Flutter app.

I use Intellij 2025.3 and the Flutter plugin 88.2.0

Best regards