Enhance MiMC test with negative validation checks

[VolodymyrBg]

Description

This PR enhances the MiMC test by adding negative validation checks to ensure the proof system correctly rejects invalid inputs. These improvements include:

1. Adding validation of random incorrect images in each test iteration
2. Adding a specific test for tampered public inputs
3. Improving error messages for failed assertions

This change strengthens the test suite by validating not only that valid proofs are accepted, but also that invalid proofs are properly rejected, which is a critical security aspect of zero-knowledge proof systems.

closes: #XXXX

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• Targeted PR against correct branch (master)
• Linked to Github issue with discussion and accepted design OR have an explanation in the PR that describes this work.
• Wrote unit tests
• Updated relevant documentation in the code
• Added a relevant changelog entry to the Pending section in CHANGELOG.md (this is a test improvement only, no functional change)
• Re-reviewed Files changed in the Github PR explorer