[exo-tflite] Introducing a pass that fuse TFLConv2D and [TFLAdd or TFLSub] (#7995)

[exo-tflite] Introducing a pass that fuse TFLConv2D and [TFLAdd or TFLSub] (#7995)

* [exo-tflite] Introducing a pass that fuse TFLConv2D and [ TFLAdd or TFLSub ]

This introduces a pass that fuse TFLConv2D and [ TFLAdd or TFLSub ]. Real fusing code will be committed in next PR.

Signed-off-by: Hyun Sik Yoon <hyunsik.yoon@samsung.com>
* renaming new_bias_node to widened_const

* removed comment that says bias of conv2d is all 0's

* fix type + use more specific node names

* stop using loco::replace(..) for widened bias const

* removed unused vars

* bug fix for set_const_input