RFR: 8310306: Pin msys2/setup-msys2 github action to a specific commit

[Jaikiran Pai]

Can I please get a review of this change which backports the fixes for https://bugs.openjdk.org/browse/JDK-8310259?

This wasn't a clean backport because this also brings in https://bugs.openjdk.org/browse/JDK-8309934 which in theory isn't a must-have change, but I think it's good to have these changes match with what's in mainline.

With this commit in this PR, the windows github actions jobs that are failing in this jdk21 repo, should now continue to pass.

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Commit messages:
 - 8310306: Pin msys2/setup-msys2 github action to a specific commit

Changes: https://git.openjdk.org/jdk21/pull/31/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21&pr=31&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8310306
  Stats: 4 lines in 2 files changed: 1 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk21/pull/31.diff
  Fetch: git fetch https://git.openjdk.org/jdk21.git pull/31/head:pull/31

PR: https://git.openjdk.org/jdk21/pull/31