* 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

* move blas related files
* move lapack related files

* move operators/math/math_function_* to pten/kernels/func
* namespace from `paddle::operators::math` to `pten::funcs`

* Enhance affine grid operator:
1. Add cuda kernel
2. Add align corners options
test=develop

* Move new affine_grid api to functional
test=develop

* Add CUDA kernel for affine_grid.
test=develop

* Add more unitest for grid sample API
test=develop

* Fix build error of affine grid op in mac os.
test=develop

* Make function return reference.
test=develop

* Add affine grid generator.

* fix ffine grid.

* Add unitest.

* Add CPU kernel and fix unitest.

* Fix CPU kernel.

* Refine code.
test=develop

* Fix python api.
test=develop

* Update python api.
test=develop

* Fix comment.
test=develop

* Rename affine_grid_generator to affine_grid and enhence unitest.
test=develop

* Fix unitest.
test=develop