[jdk21u-dev] RFR: 8310923: Refactor Currency tests to use JUnit

[Goetz Lindenmaier]

I backport this to keep the 21u test suite up-to-date. This will simplify future test backports.

-------------

Commit messages:
 - Backport e848d9471f5de86e5ac157b710cd7371f12f0024

Changes: https://git.openjdk.org/jdk21u-dev/pull/162/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=162&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/jdk21u-dev/pull/162.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/162/head:pull/162

PR: https://git.openjdk.org/jdk21u-dev/pull/162