8160127: JShell API: ExecutionControl implementation support

I think it is okay to push this version as long as certain issues are considered for follow-up work:

     ExecutionControl

    Shouldn't this have a @FunctionalInterface annotation?

Should ExecutionControl extend AutoCloseable so it can be used with try-with-resources? AutoCloseable, unlike java.io.Closeable, is not required to be idempotent.

Can we have

    JdiDefaultExecutionControl

rather than

    JDIDefaultExecutionControl

Likewise for other types whose current names start with "JDI".

...

Thanks,
-Joe