RFR: 8340401: DcmdMBeanPermissionsTest.java and SystemDumpMapTest.java fail with assert(_stack_base != nullptr) failed: Sanity check [v2]

[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 incrementally with one additional commit since the last revision:

  8340401: test for thread with uninitialized stack

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Changes:
  - all: https://git.openjdk.org/jdk/pull/21091/files
  - new: https://git.openjdk.org/jdk/pull/21091/files/5c040204..9b54225e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21091&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21091&range=00-01

  Stats: 3 lines in 1 file changed: 0 ins; 2 del; 1 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