This reverts commit b532315d.

* mv floordiv to phi

* mv elementwise_pow to phi

* fix as review

* move elementwise_div grad

* change mutable_data to alloc

* fix compile bugs

* move elementwise function to funcs directory

* fix compile bugs

* modify according to comment

* add ele_add

* add ele_mul

* add ele_sub

* sovle conflict

* fix npu

* refine ele_add

* add ele_mul unittest

* refine ele_sub

* refine ci

* refine unittest

* unify register macro

* rename declare macro

* fix infrt error

* rename pten dir to phi

* rename namespace to phi

* rename infrt pten dir to phi

* resolve conflict

* rename pten to phi in cmake

* revert all infrt change

* change needed files

* fix infrt failed

* fix inference failed

* add more op int16 support

* fix xpu ci

* clean useless header in pten core

* fix compiled failed

* fix cmake target

* fix typo

* resolve conflict

[Pten]Refactor elementwise_add grad / double grad / triple grad Kernel and move them to pten (#39048)

* refactor elementwise add grad

* fix compile bugs

* fix unit test bugs

* fix file conflicts

* fix bugs when buildPtenContext