[jdk25u-dev] RFR: 8375231: Refactor util/ServiceLoader tests to use JUnit

[Roland Mesde]

Backporting JDK-8375231, JDK-8375232 and JDK-8375233: Refactor util/ServiceLoader, util/StringJoiner and util/Vector tests to use JUnit.

This PR converts 11 TestNG tests (7 ServiceLoader, 3 StringJoiner, 1 Vector) to JUnit in a single commit.

For parity with Oracle JDK.

Ran related tests on linux-x64, linux-aarch64, macos-aarch64 and windows-x64:

make test TEST=test/jdk/java/util/ServiceLoader
make test TEST=test/jdk/java/util/StringJoiner
make test TEST=test/jdk/java/util/Vector/ArrayManagement.java

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Commit messages:
 - Backport 34705a77f9a90da5ab2a440c11d79aef7bb3ba54

Changes: https://git.openjdk.org/jdk25u-dev/pull/298/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk25u-dev&pr=298&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8375231
  Stats: 357 lines in 11 files changed: 81 ins; 53 del; 223 mod
  Patch: https://git.openjdk.org/jdk25u-dev/pull/298.diff
  Fetch: git fetch https://git.openjdk.org/jdk25u-dev.git pull/298/head:pull/298

PR: https://git.openjdk.org/jdk25u-dev/pull/298