RFR: 8375231: Refactor util/ServiceLoader tests to use JUnit [v3]

[Justin Lu]

> This PR converts the TestNG tests in _util/ServiceLoader_ (7), _util/StringJoiner_ (3), and _util/Vector_ (1) to JUnit.
> The first commit is from the automated tool, the rest are manual changes done after.
> 
> Before
> ServiceLoader: Framework-based tests: 62 = 62 TestNG + 0 JUnit
> StringJoiner: Framework-based tests: 32 = 32 TestNG + 0 JUnit
> Vector: Framework-based tests: 9 = 9 TestNG + 0 JUnit
> 
> After
> ServiceLoader: Framework-based tests: 62 = 0 TestNG + 62 JUnit
> StringJoiner: Framework-based tests: 32 = 0 TestNG + 32 JUnit
> Vector: Framework-based tests: 9 = 0 TestNG + 9 JUnit

Justin Lu has updated the pull request incrementally with two additional commits since the last revision:

 - Clean up data providers
 - Narrow down the scope of where the exception may occur

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/29210/files
  - new: https://git.openjdk.org/jdk/pull/29210/files/dedfc033..8e50c6ff

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29210&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29210&range=01-02

  Stats: 168 lines in 4 files changed: 32 ins; 70 del; 66 mod
  Patch: https://git.openjdk.org/jdk/pull/29210.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29210/head:pull/29210

PR: https://git.openjdk.org/jdk/pull/29210