RFR: 8344628: Test TestEnableJVMCIProduct.java run with virtual thread intermittent fails

[Doug Simon]

This PR prevents a rare, intermittent failure of TestEnableJVMCIProduct.java.
It does this by writing the expected test output to a file instead of stdout to avoid issues with VM error logging interleaving with the test output.

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Commit messages:
 - mitigate against interleaved output

Changes: https://git.openjdk.org/jdk/pull/22323/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22323&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8344628
  Stats: 19 lines in 1 file changed: 13 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/22323.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22323/head:pull/22323

PR: https://git.openjdk.org/jdk/pull/22323