[jdk21u-dev] RFR: 8303773: Replace "main.wrapper" with "test.thread.factory" property in test code

[Goetz Lindenmaier]

I backport this to streamline testing in 21.
I verified all files where respective tests sit nearby. Others will be used in SAP nightly testing.

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Depends on: https://git.openjdk.org/jdk21u-dev/pull/438

Commit messages:
 - Backport 89987dbf8789f166fe24e7facf5b8cc9a3c292c2

Changes: https://git.openjdk.org/jdk21u-dev/pull/444/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=444&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8303773
  Stats: 63 lines in 21 files changed: 0 ins; 1 del; 62 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/444.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/444/head:pull/444

PR: https://git.openjdk.org/jdk21u-dev/pull/444