Vendor valgrind headers

This is encouraged according to https://valgrind.org/docs/manual/manual-core-adv.html#manual-core-adv.clientreq

ConflictSet.cpp

@@ -36,10 +36,7 @@ limitations under the License.
 #include <arm_neon.h>
 #endif
 
-#if __has_include(<valgrind/memcheck.h>)
-#define MEMCHECK
-#include <valgrind/memcheck.h>
-#endif
+#include <memcheck.h>
 
 // ==================== BEGIN IMPLEMENTATION ====================
 
@@ -59,14 +56,10 @@ struct BoundedFreeListAllocator {
     }
     assert(freeList != nullptr);
     void *buffer = freeList;
-#ifdef MEMCHECK
     VALGRIND_MAKE_MEM_DEFINED(freeList, sizeof(freeList));
-#endif
     memcpy(&freeList, freeList, sizeof(freeList));
     --freeListSize;
-#ifdef MEMCHECK
     VALGRIND_MAKE_MEM_UNDEFINED(buffer, sizeof(T));
-#endif
     return new (buffer) T;
   }
 
@@ -78,16 +71,12 @@ struct BoundedFreeListAllocator {
     memcpy((void *)p, &freeList, sizeof(freeList));
     freeList = p;
     ++freeListSize;
-#ifdef MEMCHECK
     VALGRIND_MAKE_MEM_NOACCESS(p, sizeof(T));
-#endif
   }
 
   ~BoundedFreeListAllocator() {
     for (void *iter = freeList; iter != nullptr;) {
-#ifdef MEMCHECK
       VALGRIND_MAKE_MEM_DEFINED(iter, sizeof(iter));
-#endif
       auto *tmp = iter;
       memcpy(&iter, iter, sizeof(void *));
       free(tmp);