RFR: 7903553: Update GitHub checkout action to v4

[Christian Stein]

Please review this change to update to use `actions/checkout at v4` in jtreg's GHA workflows.

Find the associated release notes here: https://github.com/actions/checkout/releases/tag/v4.0.0

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Commit messages:
 - Update test.yml
 - Fix test.yml
 - Update gradle-wrapper-validation.yml
 - Update test.yml

Changes: https://git.openjdk.org/jtreg/pull/171/files
 Webrev: https://webrevs.openjdk.org/?repo=jtreg&pr=171&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903553
  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jtreg/pull/171.diff
  Fetch: git fetch https://git.openjdk.org/jtreg.git pull/171/head:pull/171

PR: https://git.openjdk.org/jtreg/pull/171