CLDRConverter run time increased by 3x

Over the course of the last two years, we've seen a more than 25% regression in build time. I've tracked this down to a handful of individual changes.

On of them is JDK-8176706, which causes build time to go up with 21 seconds on my reference machine.

The sudden increase in build time caused by JDK-8176706 needs to be analyzed, to see if it is possible to avoid.

This might (or might not) also be related to JDK-8282460, which tracks a microbenchmark performance regression of the JDK since JDK-8176706.