RFR: 8340401: DcmdMBeanPermissionsTest.java and SystemDumpMapTest.java fail with assert(_stack_base != nullptr) failed: Sanity check [v7]

[Simon Tooke]

> This PR addresses JDK-8340401 by adding a test for a thread with no stack currently assigned.

Simon Tooke has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/21091/files
  - new: https://git.openjdk.org/jdk/pull/21091/files/f8f8bbab..f71d5150

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21091&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21091&range=05-06

  Stats: 7 lines in 2 files changed: 2 ins; 2 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/21091.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21091/head:pull/21091

PR: https://git.openjdk.org/jdk/pull/21091