Dedup (aka DISTINCT) support on PhysicalPlan

[mamcx]

Description of Changes

As the title says.

Expected complexity level and risk

1

Testing

Describe any testing you've done, and any testing you'd like your reviewers to do,
so that you're confident that all the changes work as expected!

• Write a test you've completed here.
• Write a test you want a reviewer to do here, so they can check it off when they're satisfied.

[bfops]

What's the impact/purpose of this change? Could you add more info to the PR description?

@mamcx @joshua-spacetime

[mamcx]

Is not a priority for 1.0. Is to test that adding a new operator works horizontally across all the query engine