RFR: 7903045: Fix and enable test workflow using GitHub Actions

[Christian Stein]

Resolves https://bugs.openjdk.java.net/browse/CODETOOLS-7903045

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Commit messages:
 - 7903045: Fix and enable test workflow using GitHub Actions

Changes: https://git.openjdk.java.net/jtreg/pull/32/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jtreg&pr=32&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7903045
  Stats: 40 lines in 1 file changed: 11 ins; 0 del; 29 mod
  Patch: https://git.openjdk.java.net/jtreg/pull/32.diff
  Fetch: git fetch https://git.openjdk.java.net/jtreg pull/32/head:pull/32

PR: https://git.openjdk.java.net/jtreg/pull/32