RFR: 8370240: [PPC64] jhsdb jstack cannot handle continuation stub

[David Briemann]

This is a port of 8369979 for PPC. It allows to calculate caller SP from `CodeBlob` for continuation stub.
It also enables the test `test/hotspot/jtreg/serviceability/sa/TestJhsdbJstackWithVirtualThread.java` for PPC.

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

Commit messages:
 - 8370240: [PPC64] jhsdb jstack cannot handle continuation stub

Changes: https://git.openjdk.org/jdk/pull/27902/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27902&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8370240
  Stats: 17 lines in 2 files changed: 15 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/27902.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27902/head:pull/27902

PR: https://git.openjdk.org/jdk/pull/27902