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: @dayschan
Reviewed-by: @gaoxiong1,@dylangeng
Signed-off-by: @gaoxiong1

From: @r1chardf1d0
Reviewed-by: 
Signed-off-by:

1. added a pass to replace Assign with InplaceAssign.
2. bugfix in eliminate_redundant_output. the side-effect node should not be eliminated.
3. bugfix in graph_kernel/splitter.py, the kernel includes InplaceAssign should be a composite node.
4. added two tool functions GetAllInputDeviceTypes and GetAllOutputDeviceTypes into AnfAlgo.
5. do not fuse a single Assign in pass BasicOpsFusion.

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

From: @wilfchen
Reviewed-by: @cristoval,@limingqi107
Signed-off-by: @limingqi107

Cast the float16-input to float32 before ReduceSum, and cast back to float16 after ReduceSum.
If the op after this ReduceSum is a casting from float16 to float32, then it can be eliminated.

From: @jojobugfree
Reviewed-by: @kisnwang,@zhoufeng54,@chujinjin
Signed-off-by: @chujinjin

what's more:
  remove one restriction of getitem in ops fusion.
  add a while loop for the ShapeOpsSplitter pass.
  add ExpandDims into shape_ops list.

fixbug in ReplaceNewFuseCNode
add a pass to eliminate repeated output after cse
fixbug in graph_kernel_splitter
do not fuse reshape op as output in costmodel.

From: @zyli2020
Reviewed-by: 
Signed-off-by:

From: @wilfchen
Reviewed-by: @cristoval,@limingqi107
Signed-off-by: @limingqi107

From: @harsh1995
Reviewed-by: @john_tzanakakis,@wenkai_dist
Signed-off-by: @wenkai_dist

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

From: @joylvliang
Reviewed-by: @chujinjin,@jjfeing
Signed-off-by: @chujinjin

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

Refactor the BasicOpsFusion and CompositeOpsFusion to one pass.
Add a pass to eliminate the redundant output.

TODO: rename the file basic_ops_fusion and delete the file composite_ops_fusion

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

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

Other Contributor: Adel Shafiei, John Tzanakakis

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

Merge pull request !8026 from ZPaC/master-set-context-device-id