[SYCL free func] migrate MultiMarginLoss kernels

[jiafuzha]

The two SYCL kernels in this file are free functions (not class functors):
-  multi_margin_loss_forward_kernel 
-  multi_margin_loss_backward_kernel 
- They are annotated with  SYCL_EXT_ONEAPI_FUNCTION_PROPERTY((syclexp::nd_range_kernel<1>)) .

Result of  syclexp::sub_group_size  property check:

  -  syclexp::sub_group_size  is not present in this file.                                              
  - So the kernels are free-function style, but do not have the subgroup-size property.                 
                                                                                                        
 Ran related UTs:                                                                                       
                                                                                                        
  1. In  pytorch                                         
                                                                                                        
  -  pytest test/test_nn.py -v -k "MarginLoss_empty or MarginLoss_race or MarginLoss_warnings"          
  - Result: 2 passed, 3 skipped.                                                                        
                                                                                                        
  2. In current repo       
                                                                                                        
  -  pytest test/xpu/test_nn_xpu.py -v -k "MarginLoss_empty or MarginLoss_race or MarginLoss_warnings"
  - Result: 7 passed, 3 skipped (includes XPU margin-loss coverage).