Additional Validation and Conversion Tests

As part my efforts to develop [ucumate](https://fhnaumann.github.io/ucumate/), I have created more tests. The tests are available as a JSON file and include publicly available code lists (such as the fhir-common codes list) as well as extensive edge case testing. The latter causes some problems for Ucum-java. Due to the ambiguity in the UCUM specification, there are some validation differences. These are explained [here](https://fhnaumann.github.io/ucumate/ucumate_ucumjava_bridge/#functional-json-test-difference).

I have also developed [drop-in replacement layer](https://fhnaumann.github.io/ucumate/ucumate_ucumjava_bridge/) that implements the `UCUMService` interface defined here. The behavior to Ucum-java is really close, but some validation differences exist. For like 95% of the commonly used codes this is not a problem, just the edge cases behave slightly different.

I can also contribute the test suite back to this library but I am unsure what the best way is.

Should I convert the test cases to the existing XML test suite style?
And what about the validation differences?

[ucum-tests.json](https://github.com/user-attachments/files/20805888/ucum-tests.json)