<i18n dev> RFR: 8311663: Additional refactoring of Locale tests to JUnit

[Justin Lu]

Please review this PR which refactors more java.util.Locale tests to JUnit with some minor cleanup as well.

Although some of the files could benefit from being renamed bugNNNNNNN to something more descriptive, this makes reviewing harder, and will be handled separately.

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Commit messages:
 - Same as prev commit
 - Remove try catch in Bug8135061.java
 - Missing import in Bug8166994.java
 - Refactor HashCodeTest.java
 - Refactor Bug6989440.java
 - Refactor ThaiGov.java
 - Refactor UseOldISOCodesTest.java
 - Refactor FilteringModeTest.java
 - Refactor Bug8159420.java
 - Refactor Bug8166994.java
 - ... and 3 more: https://git.openjdk.org/jdk/compare/292ee630...933c0312

Changes: https://git.openjdk.org/jdk/pull/14881/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14881&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8311663
  Stats: 575 lines in 10 files changed: 173 ins; 233 del; 169 mod
  Patch: https://git.openjdk.org/jdk/pull/14881.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14881/head:pull/14881

PR: https://git.openjdk.org/jdk/pull/14881