fix: stabilize engine cache keys for unordered settings

[fs-eire]

Description

Stabilizes engine cache keys for unordered compilation settings. Set and frozenset values are canonicalized before hashing, preventing identical settings from producing different cache keys across Python processes. Includes focused test coverage.

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code follows the style guidelines of this project (You can use the linters)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas and hacks
• I have made corresponding changes to the documentation
• I have added tests to verify my fix or my feature
• New and existing unit tests pass locally with my changes
• I have added the relevant labels to my PR in so that relevant reviewers are notified