Complete Json Data Validation

[BVivek974]

This PR re-enables and updates the validation test logic that had previously been commented out.

With the validation code commented, Yangkit was not properly reporting type errors. For example:

• A boolean leaf could incorrectly accept a number or a string
• A string leaf could incorrectly accept a number
• More generally, type mismatches were not being detected during validation

By uncommenting and updating the test logic, type validation is now correctly enforced again, and all related tests are passing as expected.

Changes

• Uncommented the validation test section
• Updated the logic to align with the current implementation
• Restored proper type-checking behavior in tests

Result
All type validation tests are now passing, ensuring that incorrect data types are properly rejected according to the YANG model.