[jdk11u-dev] RFR: 8310923: Refactor Currency tests to use JUnit

[Andrew Lu]

I backport this for parity with 11.0.24-oracle.

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Commit messages:
 - Backport e848d9471f5de86e5ac157b710cd7371f12f0024
 - Backport e848d9471f5de86e5ac157b710cd7371f12f0024

Changes: https://git.openjdk.org/jdk11u-dev/pull/2625/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2625&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8310923
  Stats: 1089 lines in 9 files changed: 436 ins; 372 del; 281 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2625.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2625/head:pull/2625

PR: https://git.openjdk.org/jdk11u-dev/pull/2625