RFR: 8361602: [TESTBUG] serviceability/HeapDump/UnmountedVThreadNativeMethodAtTop.java deadlocks on exception [v4]

[Richard Reingruber]

> This pr moves the `notify()` call to the finally block to avoid the deadlock in `join()` if `verifyHeapDump(dumpFile)` throws an exception.
> 
> Testing was done with fastdebug and release builds on the main platforms and also on Linux/PPC64le and AIX.

Richard Reingruber has updated the pull request incrementally with two additional commits since the last revision:

 - Last line is incomplete (acc. to POSIX). Add newline.
 - `done` shouldn't be public

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/26213/files
  - new: https://git.openjdk.org/jdk/pull/26213/files/13cb9ba3..c2ae5b24

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26213&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26213&range=02-03

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/26213.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26213/head:pull/26213

PR: https://git.openjdk.org/jdk/pull/26213