The basic idea is: exploits data dependency to control the execution order
of side-effect operations, and keep the semantics of ANF unchanged.

The ControlDepend primitive is removed and there are two primitives added:

1. UpdateState:
```
  a = Assign(para, value)
```
became:
```
  a = Assign(para, value, u)
  u = UpdateState(u, a)
```

2. Load:
```
  x = Add(para, value)
```
became:
```
  p = Load(para, u)
  x = Add(p, value)
  u = UpdateState(u, p)
```

From: @zh_qh
Reviewed-by: @stsuteng,@chenfei52
Signed-off-by: @stsuteng

From: @chenfei52
Reviewed-by: 
Signed-off-by:

normalize codes of session

Merge pull request !8293 from 张清华/grad_opt2

Merge pull request !5918 from flywind/optimizer_pynative_memory

Merge pull request !5055 from lirongzhen1/int64

replace frontend/operator/ops.h in backend with base/core_ops.h as
backend should not use any frontend-only primitive

Signed-off-by: zhoufeng <zhoufeng54@huawei.com>

add join for ref

adjust env eliminate to eliminate all env ops

add partial app cache

resolve while endless

fix env eliminate

support for "for while" cases

fix join shape error

Merge pull request !3370 from xychow/fix-context-dup

if funcgraph or metafuncgraph call it recursively, then anf_node should be used as tracking_id to discriminate the first occurcance and the
recursive occurance.
add anf_node to PrimitiveAbstractClosure hash() to reduce cost of GetEvaluatorFor().

ignore the tracking_id to make cse work.