This reverts commit 3be79efd808f54b6e66fa45f26e601e5a143ae76, reversing
changes made to cf4479756a.

This reverts commit a2f50fb7db2fe1ae588b11e08fc51fe2398114ef, reversing
changes made to 4735ec3296.

From: @changzherui
Reviewed-by: @kingxian,@zhoufeng54
Signed-off-by: @zhoufeng54

1. set class GraphKernel as deprecated, and treat it as Cell
2. set class InplaceAssign as deprecated, suggested using Assign instead.
3. set op_selector as deprecated, removed the _selected_ops and _selected_grad_ops, replaced with real operations
4. removed the two passes of GraphKernel from frontend
5. removed the GraphKernel's codes from other modules

From: @yanzhenxiang2020
Reviewed-by: 
Signed-off-by:

From: @liu_xiao_93
Reviewed-by: @liangchenghui
Signed-off-by: @liangchenghui

From: @jiangzg001
Reviewed-by: @liangchenghui,@wuxuejian
Signed-off-by: @liangchenghui

From: @jiangzg001
Reviewed-by: @liangchenghui
Signed-off-by: @liangchenghui

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

From: @lianliguang
Reviewed-by: @zh_qh,@zh_qh,@chujinjin
Signed-off-by: @zh_qh,@zh_qh

From: @jiangzg001
Reviewed-by: @liangchenghui,@wuxuejian
Signed-off-by: @liangchenghui

A minor change in sigmoidGradGrad operation (non-functional change).

From: @liangchenghui
Reviewed-by: @c_34,@wuxuejian
Signed-off-by: @wuxuejian

check input dims for nn.LSTM.

From: @david-he91
Reviewed-by: @liangchenghui,@linqingke
Signed-off-by: @liangchenghui

From: @david-he91
Reviewed-by: 
Signed-off-by: