Operator-Controller resolution considers spec.channel

[awgreene]

Goal:
The Operator Controller should be updated to feed channel constraints into Deppy.

Background:

• When working on this ticket, it may be fruitful to review this PR, which updated the operator API to allow users to specify a spec.version constraint.

Acceptance Criteria:

• The "Demo Script" outlined in Honoring an optional spec.channel field in the Operator API. #163 runs as expected
• Reasonable testing is introduced.