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: @zhangbuxue
Reviewed-by: 
Signed-off-by:

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>

Merge pull request !3129 from hewei/decouple_ir_frontend

Merge pull request !3229 from changzherui/mod_syc_code