fix: Code Duplication in Validator Management

[MerlinTheWhiz]

Closes #147

Changes I made:

• Updated: lib.rs — made validator_utils public and gated property-based tests.
• Updated: validator_utils.rs — fixed comparator bug in remove_validator_from_list.
• Added: validator_utils_harness.rs — new focused integration test. I had to separate it because there are a lot of errors in the rest.

Screenshot of test passing:

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