Add a version number to tuistenv

[ollieatkinson]

Is your feature request related to a problem? Please describe.
At the moment there's no way to determine the version number for tuistenv. Our use-case is that we bundle tuistenv with our repository, it's important for us to be able to verify the versions of the tool people are using.

Describe the solution you'd like
tuist --env-version (tbc, willing to negotiate :D) to print it's version number

Additional context
The version number for tuist is different from tuistenv. This is even more important when we are introducing a bug fix into tuistenv.