[IDNA] Clean up GenerateIdnaTest.testCases

[cketti]

• Removes unused data and converts testCases to a simple String array
• Removes duplicate entries

This shouldn't introduce any (significant) behavior changes. The generated output is the same as it was before.

[markusicu]

Thanks!
So yes, most of the test cases used to include additional fields like in the test data output, but they were not used and thus may have been out of sync with reality.
And the last few test cases already only had the input strings.
It looks like all of the same test cases are still there, minus some duplicates.
The duplicates used to have cases for transitional vs. nontransitional processing, but again, those details were ignored.