[jdk8u-dev] RFR: 8298108: Add a regression test for JDK-8297684

[Severin Gehwolf]

Please review this backport of the regression test for a critical fix which we've included with the January CPU update. The fix was https://bugs.openjdk.org/browse/JDK-8280890

This patch adds an additional regression test which was seen in the wild with JDK 17. The patch isn't clean since the test library in jdk8u is different so needed a bit of a different setup routine for getting the jar with the provider created. Additionally, in jdk 8 the property to add providers is setting `java.ext.dirs=...` over `java.locale.providers=SPI` in later JDKs.

The test passes for me on the current dev tree.

Thoughts?

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Commit messages:
 - Add regression test for JDK-8297684

Changes: https://git.openjdk.org/jdk8u-dev/pull/269/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=269&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8298108
  Stats: 193 lines in 3 files changed: 193 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/269.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev pull/269/head:pull/269

PR: https://git.openjdk.org/jdk8u-dev/pull/269