Run pytest tests in conda builds

Description

This MR replaces !1230 (closed) by implementing pytest tests to run in conda builds during the TEST phase. This only runs pytest-compatible (pytest-discoverable) tests, and not anything else, for simplicity.

API Changes and Justification

Backwards Compatible Changes

• This change introduces no API changes
• This change adds new API calls

Backwards Incompatible Changes

• This change modifies an existing API
• This change removes an existing API

If any of the Backwards Incompatible check boxes are ticked please provide a justification why this change is necessary and why it needs to be done in a backwards incompatible way.

Review Status

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