Cycles: Add optional per-kernel performance statistics

When verbose level 4 is enabled, Blender prints kernel performance
data for Cycles on GPU backends (except Metal that doesn't use
debug_enqueue_* methods) for groups of kernels.
These changes introduce a new CYCLES_DEBUG_PER_KERNEL_PERFORMANCE
environment variable to allow getting timings for each kernels
separately and not grouped with others. This is done by adding
explicit synchronization after each kernel execution.

Differential Revision: https://developer.blender.org/D15971

intern/cycles/device/oneapi/queue.cpp

@@ -77,7 +77,7 @@ bool OneapiDeviceQueue::enqueue(DeviceKernel kernel,
 
   void **args = const_cast<void **>(_args.values);
 
-  debug_enqueue(kernel, signed_kernel_work_size);
+  debug_enqueue_begin(kernel, signed_kernel_work_size);
   assert(signed_kernel_work_size >= 0);
   size_t kernel_work_size = (size_t)signed_kernel_work_size;
 
@@ -97,6 +97,8 @@ bool OneapiDeviceQueue::enqueue(DeviceKernel kernel,
                               oneapi_device_->oneapi_error_message() + "\"");
   }
 
+  debug_enqueue_end();
+
   return is_finished_ok;
 }