[JVMCI] add helper to perform Java upcalls

In certain situations it would be useful to call up to a Java helper from generated code. Because of the way stack walking works this requires an intervening stub frame which means it has to go through the JVM. So we need a new JVMCIRuntime entry point that allows invoking a static Java method with an optional argument and possibly returning a value. The constraints were chosen for simplicity of implementation and because nothing more complex was needed.