feat(oracle): allow for specifiying config and key file from env vars

[a-dubs]

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• I have added unit tests to cover the new behavior under ``tests/unit_tests/```
• I have run tox -e format locally to automatically format my code before submitting
• I have run tox locally ensuring that it passes before submitting
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Proposed Commit Message

N/A

Description and Relevant Issues

This will allow for testing OCI on jenkins 🎉

Since the config file and the oci pem key file are stored in credentials bindings on jenkins, we need to be able to reference their paths using just environment variables, and more importantly, pycloudlib needs to be able to insert the key file path into the oci config at runtime using the key file path given to it via the new env var.

Additional Context

Test Steps

I added new unit tests for both the helper function itself and also to end-to-end test the OCI cloud constructor when environment variables are used. I generated html coverage report and ensured 100% coverage of newly added code.

Manual Testing

Ran the oracle example file using the following command and ensured via the logs that my new oci config was being read correctly:

PYCLOUDLIB_OCI_KEY_FILE_PATH="..." \                                                                                                                                     
PYCLOUDLIB_OCI_CONFIG_FILE_PATH="..." \
python examples/oracle.py

Merge type

• Squash merge using "Proposed Commit Message"
• Rebase and merge unique commits.

[a-dubs]

@mstpn ignore the first class/suite of tests in test_util.py (TestGetSubnetId) since all i did was indent and convert existing tests to be in one common class instead of individual ungrouped tests.

[mstpn]

If you can fix the pylint errors everything else looks good to me.

Thanks for cleaning up the tests for readability.

[uhryniuk]

After linter errors are sorted then you're g2g

[a-dubs]

@mstpn @uhryniuk ready for final re-review now that I fixed everything

[mstpn]

Great work here @a-dubs.