Virtual threads support

[cowwoc]

Is your feature request related to a problem? Please describe.
The heap dump produced by VisualVM, and the Thread tab in the UI, do not show virtual threads.

Describe the solution you'd like
The heap dump should show virtual threads and their associated stack-trace (e.g. jcmd <pid> Thread.dump_to_file <file>). The Thread UI tab should show virtual threads.

[cowwoc]

Other UX suggestions:

Provide options for the following functionality:

1. Groups all threads with similar stack-traces (as IntelliJ does).
2. Sort threads by their runtime duration, to identify potentially stuck/deadlocked threads.
3. We should be able to reorder threads in an existing dumps, instead of having to generate a new dump (because maybe the process is dead by this point).

[cowwoc]

You can get a list of all virtual threads with a mix of jdk.internal.vm.ThreadContainers and jdk.internal.vm.ThreadContainer.threads() using reflection. I know that invoking private APIs is not ideal, but I don't think there is an alternative at the moment.

Once you have a list of virtual threads, you should be able to include them in heap dumps as well as show the local variables per stack frame.

[cowwoc]

Hi again. Are you planning to work on Virtual Threads now that they are targeted as non-preview for JDK 21, and you just cut a new release of VisualVM?

[thurka]

While reading through the specification JEP 444: Virtual Threads, I filed in the following enhacements:
GH-501
GH-502
GH-503
GH-504
GH-507

[sureshg]

Hi, are there any plans to add support for the virtual thread soon?

[codylilidp]

Fixing #549 seems to be critical for virtual threads support.

[AlanBateman]

Virtual threads are included in HPROF heap dumps since JDK 22 (JDK-8321565).

[thurka]

Virtual threads are included in HPROF heap dumps since JDK 22 (JDK-8321565).

This is supported by VisualVM since 2.1.8 (GH-539).