See discussion at: https://mail.openjdk.org/pipermail/panama-dev/2024-November/020802.html

The text at: https://docs.oracle.com/en/java/javase/23/docs/specs/jvmti.html#heapCallbacks

list several restrictions on heap callbacks. We should add an additional restriction saying that a heap callback can not point to an FFM upcall stub.