Test decomposition that contain more than one starter and ends with a non-starter followed by low-CCC non-starter

[hsivonen]

ICU4X had a bug in the normalizer for the case where a character whose decomposition contains more than one starter and ends with a non-starter is followed by a non-starter whose CCC is lower than the final non-starter of the decomposition.

I had thought about this case, but I had failed to type a ! for logical negation of a condition and the test suite didn't catch this.

NormalizationTest.txt should include cases like this. Known examples:

• NFKD of 01C4 0323
• NFD of 0DDD 0334

[hsivonen]

CC @eggrobin