[scudo] Add GWP-ASan state/metadata pointer proxies.

[hctim]

Summary

Provide accessor proxies for the gwp-asan regions that are useful in
symbolizing dumps offline. Should be useful for Fuchsia to be able to
locate these internal pointers to stash the data in a minidump.

compiler-rt/lib/scudo/standalone/combined.h

#ifdef GWP_ASAN_HOOKS
 
     GuardedAllocSlotSize =
         GuardedAlloc.getAllocatorState()->maximumAllocationSize();
     Stats.add(StatFree, static_cast<uptr>(Opt.MaxSimultaneousAllocations) *
                             GuardedAllocSlotSize);
 #endif // GWP_ASAN_HOOKS
   }
 
+#ifdef GWP_ASAN_HOOKS
+  const gwp_asan::AllocationMetadata *getGwpAsanAllocationMetadata() {
+    return GuardedAlloc.getMetadataRegion();
+  }
+
+  const gwp_asan::AllocatorState *getGwpAsanAllocatorState() {
+    return GuardedAlloc.getAllocatorState();
+  }
+#endif // GWP_ASAN_HOOKS
+
   ALWAYS_INLINE void initThreadMaybe(bool MinimalInit = false) {
     TSDRegistry.initThreadMaybe(this, MinimalInit);
   }
 
   void unmapTestOnly() {
     TSDRegistry.unmapTestOnly(this);
     Primary.unmapTestOnly();
     Secondary.unmapTestOnly();