[jdk21u-dev] RFR: 8304839: Move TestScaffold.main() to the separate class DebugeeWrapper

[Goetz Lindenmaier]

I backport this to streamline the tests in 21 and simplify later backports.

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Commit messages:
 - Backport ee9776fa23e2287b704d4f1a55179e83516d1e4c

Changes: https://git.openjdk.org/jdk21u-dev/pull/438/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=438&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8304839
  Stats: 245 lines in 19 files changed: 124 ins; 87 del; 34 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/438.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/438/head:pull/438

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