Chore: make console width deterministic in tests

[georgesittas]

I tried running pytest -n auto tests/cli/test_cli.py from a different system, locally, and started seeing assertion errors related to line break positioning:

FAILED tests/cli/test_cli.py::test_plan_dev_longnames - AssertionError: assert 'sqlmesh_example__dev_butamuchlongerenvironmentname.seed_cccccccccccccccccccccccc\ncccccccccccccccccccccccccccccccccccccccccccccccccccccccc_model          [ins...
FAILED tests/cli/test_cli.py::test_plan_nonbreaking_noautocategorization - AssertionError: assert '[1] [Breaking] Backfill sqlmesh_example.incremental_model and indirectly \nmodified children' in '.\n=========================================================...
FAILED tests/cli/test_cli.py::test_run_cron_not_elapsed - AssertionError: assert 'No models are ready to run. Please wait until a model `cron` interval has \nelapsed.\n\nNext run will be ready at ' in 'No models are ready to run. Please wai...
FAILED tests/cli/test_cli.py::test_init_interactive_engine_install_msg - assert 'Run command in CLI to install your SQL engine\'s Python dependencies: pip \ninstall "sqlmesh[gcppostgres]"' in '──────────────────────────────\nWelcome to SQLMesh!\n─────────...

Similarly, some other tests failed in the suite. Ultimately, it appears that the rich console inherited my environment's $COLUMNS which wasn't 80 and that resulted in said behavior.