RFR(XS): 8245913: JDI and JDWP ThreadReference::stop should only allow ThreadDeath

[serguei.spit...@oracle.com]

Please, review a fix for:
  https://bugs.openjdk.java.net/browse/JDK-8245913

CSR draft (one CSR reviewer is needed before finalizing it):
  https://bugs.openjdk.java.net/browse/JDK-8245923

Webrev:
  http://cr.openjdk.java.net/~sspitsyn/webrevs/2020/jdwp-stop-thread.1/src/


Updated JDI ThreadReference:stop method spec:
  http://cr.openjdk.java.net/~sspitsyn/webrevs/2020/jdwp-stop-thread.1/docs/api/jdk.jdi/com/sun/jdi/ThreadReference.html#stop(com.sun.jdi.ObjectReference)


Updated JDWP ThreadReference:Stop command spec:
  http://cr.openjdk.java.net/~sspitsyn/webrevs/2020/jdwp-stop-thread.1/docs/specs/jdwp/jdwp-protocol.html#JDWP_ThreadReference_Stop


Summary:
  The RFR+CSR for JVMTI StopThread has been posted to the serviceability-dev mailing list.
  This is a JPDA (JDI+JDWP) related spec update.
  One question is if it is okay to refer to the ThreadDeath as an Exception while, in fact, it is an Error.
  This update follows the initial JVM TI StopThread spec terminology.

Testing:
  Built docs and checked the doc has been generated as expected.
  Will run the JDI/JDWP tests locally.
  Will submit hs-tiers1-5 to make sure there are no regressions in the JDI/JDWP tests.

Thanks,
Serguei