After #90, the SnowInstance is now created at import time.

I don't think this is good as:

1. The instance must be running at import time. Some libraries, like BrowserGym, might have multiple benchmarks, so this will likely affect every run of the library, even if WorkArena is not launched.
2. All the task accept an instance at init (good!), allowing other libraries to self create the instance (so env variables might not be present, or some other process must be done first)

As this is only to get some constants that are used inside the Dashboard task, I suggest to move this code inside init function.