This RFE upstreams a few improvements for AOT heap object handling from the Leyden repo to the JDK mainline. These are prerequisites for JDK-8335368 - Ahead-of-Time Code Compilation

[1] Make the hashtable HeapShared::archived_object_cache() GC safe. This is required to support the upcoming AOT code compiler, which needs to consult this hashtable outside of a safepoint, where GCs may happen.

[2] Consolidate two versions of is_interned_string() into one.

[3] Remove the DumpedInternedStrings class which has been made redundant by JDK-8377339

[4] Added some statistics