RFR: 8370974: Command-line Hotspot debugger tests fail on Windows AArch64

[Saint Wesonga]

The registers are all shown to have the value 0. The addThreads method needs to fill the array of registers with values from the native OS CONTEXT. The clhsdb* tests now pass with this change.

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Commit messages:
 - Check return value
 - Fix Windows-AArch64 clhsdb test failures

Changes: https://git.openjdk.org/jdk/pull/28080/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28080&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8370974
  Stats: 44 lines in 1 file changed: 44 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/28080.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28080/head:pull/28080

PR: https://git.openjdk.org/jdk/pull/28080