[jdk21u-dev] RFR: 8349348: Refactor ClassLoaderDeadlock.sh and Deadlock.sh to run fully in java

[Goetz Lindenmaier]

I backport this for parity with 21.0.8-oracle,

-------------

Commit messages:
 - Backport 32d6d031514be9cfee5b0fd778cb738b7ff9d770

Changes: https://git.openjdk.org/jdk21u-dev/pull/1678/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1678&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8349348
  Stats: 189 lines in 4 files changed: 12 ins; 172 del; 5 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1678.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1678/head:pull/1678

PR: https://git.openjdk.org/jdk21u-dev/pull/1678