fix: Compatibility layer will prefer to return DelayFrames, then DelayQubits, then Delay.

[mac01021]

Description

Insert your PR description here. Thanks for contributing to pyQuil! 🙂

Checklist

• The PR targets the master branch
• The above description motivates these changes.
• The change is atomic and can be described by a single commit (your PR will be squashed on merge).
• All changes to code are covered via unit tests.
• Parameters and return values have type hints with PEP 484 syntax.
• Functions and classes have useful Sphinx-style docstrings.
• (New Feature) The docs have been updated accordingly.
• (Bugfix) The associated issue is referenced above using auto-close keywords.

[MarquessV]

Thanks for being proactive about this! I have a few follow-up questions.