message: Add a safety barrier between buffer fills and copies
  * It's unclear if this should be required as the fills and copies don't overlap,
  but this is not so perf sensitive that a barrier can't be added for safety.
diff: @@ -2137,8 +2137,25 @@ void WrappedVulkan::Apply_InitialState(WrappedVkRes *live, const VkInitialConten
  RDCDEBUG("Apply_InitialState (Mem %s): %d fills, %d copies", ToStr(orig).c_str(), fillCount,
  regions.size());
  if(regions.size() > 0)
  + {
  + VkBufferMemoryBarrier bufBarrier = {
  + VK_STRUCTURE_TYPE_BUFFER_MEMORY_BARRIER,
  + NULL,
  + VK_ACCESS_TRANSFER_WRITE_BIT,
  + VK_ACCESS_TRANSFER_WRITE_BIT,
  + VK_QUEUE_FAMILY_IGNORED,
  + VK_QUEUE_FAMILY_IGNORED,
  + Unwrap(dstBuf),
  + 0,
  + VK_WHOLE_SIZE,
  + };
  +
  + // be conservative about whether or not the above fills overlap with the below copies
  + DoPipelineBarrier(cmd, 1, &bufBarrier);
  +
  ObjDisp(cmd)->CmdCopyBuffer(Unwrap(cmd), Unwrap(srcBuf), Unwrap(dstBuf),
  (uint32_t)regions.size(), regions.data());
  + }
  VkMarkerRegion::End(cmd);
  