[jdk11u-dev] RFR: 8268185: Update GitHub Actions for jtreg 6 [v2]

[George Adams]

> simple backport of [JDK-8268185](https://bugs.openjdk.java.net/browse/JDK-8268185): Update GitHub Actions for jtreg 6 in preparation for the GitHub action rewrite backport

George Adams has updated the pull request incrementally with one additional commit since the last revision:

  Backport 3482cb87fd94e6445ca243722851daa90c00a2c8

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Changes:
  - all: https://git.openjdk.org/jdk11u-dev/pull/1239/files
  - new: https://git.openjdk.org/jdk11u-dev/pull/1239/files/b3bd517c..90a9c2ff

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1239&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1239&range=00-01

  Stats: 19 lines in 9 files changed: 0 ins; 1 del; 18 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1239.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1239/head:pull/1239

PR: https://git.openjdk.org/jdk11u-dev/pull/1239