RFR: 8315364: Assert thread state invariant for JFR stack trace capture [v3]

[Markus Grönlund]

> Greetings,
> 
> A JavaThread running in state _thread_in_native cannot capture a JFR stack trace because tagging of artefacts (klasses, methods, etc.) is a function of an epoch, which evolves during safepoints.
> 
> Asserting this invariant would have helped prevent the issue detailed in [JDK-8315220](https://bugs.openjdk.org/browse/JDK-8315220).
> 
> Testing: jdk_jfr
> 
> Thanks
> Markus

Markus Grönlund has updated the pull request incrementally with one additional commit since the last revision:

  assert negated state

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15491/files
  - new: https://git.openjdk.org/jdk/pull/15491/files/194f1c75..623505ad

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15491&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15491&range=01-02

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/15491.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15491/head:pull/15491

PR: https://git.openjdk.org/jdk/pull/15491