feat: install interpreters only when necessary

[dephekt]

Add a check if the proposed version is already installed prior to installing a given python interpreter. Each item in pyenv_python_versions will be checked if it's contained in the output of pyenv versions. If the item was in the output, the execution of the install command will be skipped. Versions not already installed will still be installed during the looping.

Fixes #57

[dephekt]

Probably needs something similar in tasks/versions/python_versions_with_homebrew.yml but since I don't use homebrew and am not familiar with it, I didn't do any testing with that.

I installed my PR branch role on my local machine to test that my reported issue is fixed by this. I'm not incredibly familiar with Travis tests, so I have not added any test to reproduce the issue and I don't understand why the current idempotency test is not failing for this scenario like I'd expect.

Before:

TASK [ansible_pyenv : Install Python interpreters] *****************************************
failed: [localhost] (item=3.10.3) => {"ansible_loop_var": "item", "changed": true, "cmd": "/home/dephekt//.pyenv/bin/pyenv install 3.10.3", "delta": "0:00:00.024369", "end": "2022-10-21 02:15:19.618294", "item": "3.10.3", "msg": "non-zero return code", "rc": 1, "start": "2022-10-21 02:15:19.593925", "stderr": "pyenv: /root/.pyenv/versions/3.10.3 already exists", "stderr_lines": ["pyenv: /root/.pyenv/versions/3.10.3 already exists"], "stdout": "", "stdout_lines": []}

After:

TASK [ansible_pyenv : Install python versions with Git install] *********************************
included: /home/dephekt/.ansible/roles/ansible_pyenv/tasks/versions/python_versions_with_git.yml for localhost

TASK [ansible_pyenv : Check if interpreters installed] ******************************************
changed: [localhost]

TASK [ansible_pyenv : Install Python interpreters] **********************************************
changed: [localhost] => (item=3.8.14)
ok: [localhost] => (item=3.7.14)
changed: [localhost] => (item=2.7.18)