From: @yeyunpeng2020
Reviewed-by: @ddwsky,@zhanghaibo5
Signed-off-by: @ddwsky

From: @oacjiewen
Reviewed-by: @gemini524,@liangchenghui,@c_34
Signed-off-by: @liangchenghui,@c_34

From: @ouyang_xx
Reviewed-by: @oacjiewen,@c_34
Signed-off-by: @c_34

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

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: @hanhuifeng2020
Reviewed-by: @gaoxiong1,@dylangeng
Signed-off-by: @dylangeng

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

From: @xutianchun
Reviewed-by: @zhanghaibo5,@hangangqiang
Signed-off-by: @zhanghaibo5,@hangangqiang

Signed-off-by: zhupuxu <zhupuxu@huawei.com>

From: @zhangzhaoju
Reviewed-by: @zh_qh,@hwhewei,@zh_qh
Signed-off-by: @zh_qh,@zh_qh

From: @zhaozhenlong
Reviewed-by: @hangangqiang,@zhanghaibo5
Signed-off-by: @hangangqiang

From: @caojian05
Reviewed-by: @oacjiewen,@wuxuejian
Signed-off-by: @wuxuejian

From: @hfarahat
Reviewed-by: @robingrosman,@pandoublefeng
Signed-off-by: @robingrosman

From: @islam_amin
Reviewed-by: @john_tzanakakis,@john_tzanakakis,@tom__chen
Signed-off-by: @john_tzanakakis

From: @hfarahat
Reviewed-by: @nsyca,@mikef,@robingrosman
Signed-off-by: @robingrosman

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

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

From: @laiyongqiang
Reviewed-by: @jjfeing,@majorzhang
Signed-off-by: @majorzhang

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

From: @yuchaojie
Reviewed-by: @jjfeing,@zhoufeng54
Signed-off-by: @zhoufeng54

From: @c_34
Reviewed-by: @zhunaipan,@oacjiewen
Signed-off-by: @oacjiewen

From: @sunsuodong
Reviewed-by: @xsmq,@jpc_chenjianping
Signed-off-by: @jpc_chenjianping

From: @yuzhenhua666
Reviewed-by: @c_34,@oacjiewen
Signed-off-by: @c_34

Unstack 使用线程池代替手动起线程

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