Mock validation

[bergman]

TL;DR

Add some simple validation to mocks

• [X] throw an exception if a mock was not used
• [X] throw an exception if a duplicate mock was already defined
• [ ] ~throw an exception if a mock was not found and not explicitly configured to run actual task~
• [X] test behaviour of unmocked SdkRunnableTask tasks (they run by default if task type has no mocks defined)

Improve error messages around mocks,

Type

• [ ] Bug Fix
• [ ] Feature
• [ ] Plugin

Are all requirements met?

• [ ] Code completed
• [ ] Smoke tested
• [ ] Unit tests added
• [ ] Code documentation added
• [ ] Any pending items have an associated Issue

Complete description

How did you fix the bug, make the feature etc. Link to any design docs etc

Tracking Issue

Remove the 'fixes' keyword if there will be multiple PRs to fix the linked issue

fixes https://github.com/flyteorg/flyte/issues/

Follow-up issue

NA OR https://github.com/flyteorg/flyte/issues/

[honnix]

I converted this to a draft, and please feel free to continue or close.

[RRap0so]

Closing since it's very out of date. Feel free to re-open if still relevant.