8205132: Remove Thread.countStackFrames()

[Alan Bateman]

Thread::countStackFrames has been deprecated for 20+ years and has been 
marked for-removal since Java SE 9. I'd like to remove it for Java SE 
14. It's was never a well-defined method and I've been unable to find 
anything that uses it. The StackWalker API is a much better solution for 
code that is interested in the number of stack frames.

The changes to remove this method are here:
    http://cr.openjdk.java.net/~alanb/8205132/webrev/

The CSR will need a Reviewer:
    https://bugs.openjdk.java.net/browse/JDK-8232654

-Alan