Use more cloud defaults in integration tests

[TheRealFalcon]

Proposed Commit Message

Use more cloud defaults in integration tests

Stop requiring compartment_id for OCI and project_id for GCE since they
can now be inferred in pycloudlib.

Additional Context

n/a

Test Steps

Remove: GCE_PROJECT, GCE_REGION, GCE_ZONE, and OCI_COMPARTMENT_ID from user_settings.py if they exist there.
Run any integration test using GCE or OCI and it should pass.

Checklist:

• My code follows the process laid out in the documentation
• I have updated or added any unit tests accordingly
• I have updated or added any documentation accordingly

[TheRealFalcon]

@OddBloke Now that canonical/pycloudlib#87 is merged, this should work. I doubled checked by running both GCE and OCI runs without any cloud-specific details in my user_settings.py

[OddBloke]

Thanks!