message: micro: Show memory plan if preprocessor define set
  Changes MicroAllocator to call GreedyMemoryPlanner::PrintMemoryPlan when
  the TF_LITE_SHOW_MEMORY_USE preprocessor symbol is defined. The
  motivation is to make it possible for developers to show the memory plan
  without needing to modify TfLM source code.
  TF_LITE_SHOW_MEMORY_USE is a new preprocessor symbol. It is not used
  elsewhere.
diff: @@ -1080,6 +1080,9 @@ TfLiteStatus MicroAllocator::CommitStaticMemoryPlan(
  TF_LITE_ENSURE_STATUS(CommitPlan(error_reporter_, &planner,
  memory_allocator_->GetHeadBuffer(),
  allocation_info, allocation_info_count));
  +#ifdef TF_LITE_SHOW_MEMORY_USE
  + planner.PrintMemoryPlan(error_reporter_);
  +#endif
  head_usage = planner.GetMaximumMemorySize();
  // The head is used to store memory plans for one model at a time during the
  