Proposal: top level test and command separation

[Kyle-Verhoog]

In order to achieve command running and test running separation a riotfile.py like the following would be required:

from riot import Venv

venv = Venv(
  venvs=[
     Venv(
         # Define tests
     ),
     Venv(
         skip_install=True,
         print_summary=True,
         venvs=[
             # Define mypy, black, etc
         ]
     ),
  ]
)

This proposal is for there to be syntactic sugar for this with something like the following:

from riot import Venv

# Have summary printed after running
# Builds local package
tests = [
   Venv(
       name="pytest",
       # ...
   )
]

# Don't have summaries printed
# Don't build local package
commands = [
  Venv(
    name="mypy",
    # ...
  )
]