* add max_p without test

* add test of max_p

* make max_p consistent with paddle.maximum

* add select_p

* fix bugs

* add custom test for select_p; modify select_p primrules

* modify according to xiaoxu's comment

* add eq_p, select_p, pow_p, use autograd to test grad of high order

* add requirement of autograd, modify expected type of eq

* modify according to xiaoxu's comment

* import primops to use primops.pow

* add log_p for auto_grad

* add log_p_op.cc in prim_op_test srcs

* fix bug of wrong op name; add test in test_primops

* add test case of log in testprimapi

* fix bug of test_without_guard

* no need to fix test_without_guard

* hide prim2orig in executor

* add some test cases without param guard

* fix spell error param into program

* Use absolute path when import paddle.incubate.autograd.prim2orig

* move _gradients to primapi and rename to grad

* modify jvp to call forward_grad in primitive mode

* add primapi unittest and remove some unused test cases.

* fix  circular import problem

* move paddle/autograd/functional into paddle/incubate.autograd/functional

* remove unused JacobianBatchLast class

* enable Jacobian,Hessian supporting new autograd

* fix prim mode failed in PR-CI-Windows

* add forward_gradients api

* add forward_gradients api

* skip test_autograd_functional_prim in windows ci

* fix test_autograd_funciton_prim timeouot

* remove the block parameter in prim2orig method

* remove duplicate to_tensors code snippet # test=allcases