Change OnPrem -> SelfHosted, But Preserve Backward Compatibility

[davidvonthenen]

Proposed changes

Addresses: #405

This attempts to preserve backward compatibility with the user's code. The default will use the new "SelfHosted" names for classes.

Types of changes

What types of changes does your code introduce to the community Python SDK?
Put an x in the boxes that apply

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update or tests (if none of the other choices apply)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• I have read the CONTRIBUTING doc
• I have lint'ed all of my code using repo standards
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments

NA