RFR: 8377656: JUnit test java/util/zip/ZipFile/ZipFileInputStreamSkipTest.java uses private methods for BeforeAll/AfterAll

[Jaikiran Pai]

Can I please get a review of this test-only fix which addresses a test issue in `test/jdk/java/util/zip/ZipFile/ZipFileInputStreamSkipTest.java`? As noted in https://bugs.openjdk.org/browse/JDK-8377656, the test uses `private` methods for `@BeforeAll`/`@AfterAll` which is discouraged by JUnit.

With the recent upgrade of jtreg https://bugs.openjdk.org/browse/JDK-8376355 such warnings now intentionally cause test failures. This wasn't caught during the integration of JDK-8376355  because the CI run for JDK-8376355 was done prior to the recent changes of these `java/util/zip` tests from testng to junit in https://bugs.openjdk.org/browse/JDK-8377116.

I've first reproduced this failure locally and then reran the tests under `java/util/zip` with this change and they all pass now. tier1 testing is currently in progress and I'll integrate this once that completes.

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

Commit messages:
 - 8377656: JUnit test java/util/zip/ZipFile/ZipFileInputStreamSkipTest.java uses private methods for BeforeAll/AfterAll

Changes: https://git.openjdk.org/jdk/pull/29670/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29670&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8377656
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/29670.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29670/head:pull/29670

PR: https://git.openjdk.org/jdk/pull/29670