Replace deprecated test functions

[marcoesters]

Description

conda.testing.integration.run_command has been deprecated. Use conda.testing.fixtures.conda_cli instead.

Checklist - did you ...

• Add a file to the news directory (using the template) for the next release's release notes?
• Add / update necessary tests?
• Add / update outdated documentation?

[kenodegard]

Several observations:

1. conda_cli is a pytest fixture and thus cannot be called directly
2. While we can import it as you've done here to expose the fixture to all tests in this file it is preferred to use the pytest_plugins constant to keep linters happy https://docs.pytest.org/en/stable/how-to/writing_plugins.html#requiring-loading-plugins-in-a-test-module-or-conftest-file
3. I suggest replacing new_environment with the tmp_env fixture instead

[marcoesters]

Several observations:

1. `conda_cli` is a pytest fixture and thus cannot be called directly

2. While we can import it as you've done here to expose the fixture to all tests in this file it is preferred to use the `pytest_plugins` constant to keep linters happy https://docs.pytest.org/en/stable/how-to/writing_plugins.html#requiring-loading-plugins-in-a-test-module-or-conftest-file

3. I suggest replacing `new_environment` with the `tmp_env` fixture instead

I realized that a little too late. Using the tmp_env fixture will take a little more rewriting, but it is necessary to not have the tests break.

[marcoesters]

I ended up using the conda_cli fixture instead of tmp_env because the tests monitor the output stream. Menuinst exceptions do not result in a non-zero exit code, but should result in a test failure.