Introduce verification code to ensure that C2 nodes have a non-null address type (Node::adr_type()) if they use and/or define memory, and a null address type otherwise. Whether a node uses or defines memory can be tested by checking the type of its inputs and outputs. Ensure the current C2 representation is consistent at key compilation points (e.g. at the end of platform-independent optimizations, or before scheduling, where the address type is used for alias analysis).

This RFE is motivated by JDK-8347901, which (unnoticedly) changed the address type of the pure call nodes after final graph reshaping: before the change, adr_type() was set to nullptr; after the change, it is set to rawptr:BotPTR. This effect is likely harmless, but it would be good to have a mechanism to catch and prevent such inconsistencies.