RFR: 8304839: Move TestScaffold.main() to the separate class DebugeeWrapper [v3]

[Leonid Mesnik]

> The code related to virtual threads support is moved into a separate class DebugeeWrapper.
> 
> The code of method main() remains the same. I don't mix code change with moving code between files.
> 
> Tesed by running 
> make run-test JTREG_RETAIN=all  TEST=com/sun/jdi
> make run-test JTREG_RETAIN=all  JTREG_TEST_THREAD_FACTORY=Virtual TEST=com/sun/jdi
> locally and tier1 and hs-tier5 in Mach5 CI

Leonid Mesnik has updated the pull request incrementally with one additional commit since the last revision:

  fixed

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15874/files
  - new: https://git.openjdk.org/jdk/pull/15874/files/f2be8210..dd6b01ff

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15874&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15874&range=01-02

  Stats: 12 lines in 2 files changed: 0 ins; 2 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/15874.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15874/head:pull/15874

PR: https://git.openjdk.org/jdk/pull/15874