RFR: JDK-8302595: use-after-free related to GraphKit::clone_map

[Justin King]

`GraphKit::clone_map` duplicates `SafePointNode` and calls `Compile::record_for_igvn`. In some cases `SafePointNode` is not used so `Node::destruct` is called to cleanup. The `Unique_Node_List` returned by `Compile::for_igvn` still references the node which resides in freed memory which may or may not have been reused. We additionally need to remove the node from `Unique_Node_List` as well to prevent this from happening.

I introduced `GraphKit::destruct_map_clone` which undoes `GraphKit::clone_map`. It even clears the type, though I am not sure if this is necessary so feel free to suggest otherwise. Additionally it calls `delete` on `JVMState`, which is a noop, but it seems like the correct thing to do in case its ever changed.

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Commit messages:
 - use-after-free related to GraphKit::clone_map

Changes: https://git.openjdk.org/jdk/pull/12578/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12578&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8302595
  Stats: 50 lines in 7 files changed: 44 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/12578.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12578/head:pull/12578

PR: https://git.openjdk.org/jdk/pull/12578