8309346: Extend hs_err logging for all VM operations deriving from VM_GC_Operation

Reviewed-by: tschatzl, stefank

src/hotspot/share/gc/shared/gcVMOperations.cpp

@@ -68,6 +68,10 @@ VM_GC_Operation::~VM_GC_Operation() {
   ch->soft_ref_policy()->set_all_soft_refs_clear(false);
 }
 
+const char* VM_GC_Operation::cause() const {
+  return GCCause::to_string(_gc_cause);
+}
+
 // The same dtrace probe can't be inserted in two different files, so we
 // have to call it here, so it's only in one file.  Can't create new probes
 // for the other file anymore.   The dtrace probes have to remain stable.

src/hotspot/share/gc/shared/gcVMOperations.hpp

@@ -137,6 +137,8 @@ class VM_GC_Operation: public VM_GC_Sync_Operation {
   }
   ~VM_GC_Operation();
 
+  virtual const char* cause() const;
+
   // Acquire the Heap_lock and determine if this VM operation should be executed
   // (i.e. not skipped). Return this result, and also store it in _prologue_succeeded.
   virtual bool doit_prologue();