RFR: 8309146: extend JDI StackFrame.setValue() and JDWP StackFrame.setValues minimal support for virtual threads

[Chris Plummer]

The JDWP spec for StackFrame.SetValue currently states:

        "If the thread is a virtual thread then this command can be used to set "
        "the value of local variables in the top-most frame when the thread is "
        "suspended at a breakpoint or single step event. The target VM may support "
        "setting local variables in other cases."

The JDI spec for StackFrame.setValue() has similar wording. In [JDK-8308814](https://bugs.openjdk.org/browse/JDK-8308814) the JVMTI spec clarified support to be for a thread suspended at any event, not just a breakpoint or single step. That same clarification is needed in the JDWP and JDI specs. No implementation changes are needed.

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Commit messages:
 - Clarify minimal suppoert for StackFrame.GetValue.

Changes: https://git.openjdk.org/jdk/pull/14235/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14235&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8309146
  Stats: 5 lines in 2 files changed: 0 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/14235.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14235/head:pull/14235

PR: https://git.openjdk.org/jdk/pull/14235