RFR: 8335630: Crash if Platform::exit called with fullScreen Stage on macOS 14 [v2]

[Kevin Rushforth]

> This PR solves two related bugs that are caused by events being delivered while the FX runtime is in the process of shutting down. These bugs are related enough that I think they need to be addressed at the same time. While debugging and developing the test, I saw one or the other or both in various test runs. The system test included with this program verifies that there is no crash and no exception, so will catch either failure mode.
> 
> This can happen when there is a full-screen window showing during shutdown on macOS, since full screen enter / exit uses a nested event loop that affects the order of operation. This could theoretically happen in other cases, thus the fix does not involve checking whether we are in full-screen or whether there is a nested event loop.
> 
> The fix does the following:
> 
> 1. `GlassWindow+Overrides.m`: Check that the JVM is still running before calling the Java notification method in `windowDidResignKey` and `windowShouldClose`. This matches what is already done for other similar methods in this class. This is the fix for JDK-8335630.
> 2. `Window.java` and `View.java`: Check whether the Application instance is null in the event notification callbacks, and skip handling the event if it is. This is the fix for JDK-8299738.
> 
> Note that the fix for 2 is in platform-independent code. This should be fine, since we would want to skip the event handling callback on any other platform if it were done during shutdown, in order to avoid the ISE.
> 
> I have included a system test that passes on all platforms. On macOS, the test will fail without the fix and pass with the fix.
> 
> Details of the fix are below:
> 
> `Platform::exit` is called by the application to shutdown the JavaFX toolkit. The implementation of `Platform::exit` calls `Toolkit::exit` on the JavaFX Application thread, which in turn calls glass `Application::terminate` to shut it down. `Application::terminate` will close all the native windows, and call `finishTerminating` to terminate the native event loop and detach the thread from the JVM. This is asynchronous, at least on macOS, and will schedule the termination by posting a native event to the event loop.
> 
> on macOS 13, and sometimes on macOS 14, a Window or View event handler can be called between `Toolkit::exit`/`Application::terminate` (which sets the Toolkit's cached thread to null and the glass Application instance to null) and the JVM shutdown. This will make a JNI upcall to the appropriate Window or View `handleXxxxx` method, which...

Kevin Rushforth 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. The pull request contains four additional commits since the last revision:

 - Merge remote-tracking branch 'upstream/master' into 8335630-exit-fullscreen
 - Revert "Debug prints"
   
   This reverts commit 0e634b7a14da19175c2b30e17a64e96e37451af2.
 - Debug prints
 - 8335630: Crash if Platform::exit called with fullScreen Stage on macOS 14
   8299738: ISE if Platform::exit called with fullScreen Stage on macOS 13

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Changes:
  - all: https://git.openjdk.org/jfx/pull/1506/files
  - new: https://git.openjdk.org/jfx/pull/1506/files/43448703..ee7841f1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1506&range=01
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1506&range=00-01

  Stats: 349763 lines in 7157 files changed: 184133 ins; 107646 del; 57984 mod
  Patch: https://git.openjdk.org/jfx/pull/1506.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1506/head:pull/1506

PR: https://git.openjdk.org/jfx/pull/1506