Add json output to conda env create/update

[beenje]

This PR adds json output to the conda env create/update commands.

Some things I'm not sure about:

1. I had to import conda.exports in conda_env/cli/main.py. Otherwise when it is imported in conda_env/pip_util.py it resets the context.

2. In my tests, if I keep the same environment name "env-1", each test passes when I run them individually. But they all fail when run together (running pytest -v tests/conda_env/test_cli.py::IntegrationTests). I had to use a different env name for each test. The setUp and tearDown fixtures seem to run properly. At one point I saw that when trying to run pip in the environment env-1/bin/python didn't exist. There was only the env-1/conda-meta directory. Could some files be deleted by the fixture after the test starts?
   Anyway I'm quite sure this is not related to my changes, but an existing issue (in the tests).

[msarahan]

Thanks @beenje, merging.

[github-actions]

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