remove SharedDDP as it is deprecated (#25702)
* remove SharedDDP as it was drepracated
* apply review suggestion
* make style
* Oops,forgot to remove the compute_loss context manager in Seq2SeqTrainer.
* remove the unnecessary conditional statement
* keep the logic of IPEX
* clean code
* mix precision setup & make fixup
---------
Co-authored-by: statelesshz <jihuazhong1@huawei.com>
