since w1a2 is coming

[Test] Changed verification method to a check if all tensor shapes are set and the output of the new node has specific value

[Test] Test for shape inference creates now a mixed model and performs shape inference. Afterwards it is executed to check if it still works

[Execution/Test] Added shape inference for custom nodes and fixed some pre-commit errors in the test files

[Test] Added first draft of shape inference test and onnx model in data path with one custom and one standard node

[Integration] Changed the position of the if condition to prevent the function building a unnecessary graph and shortened the custom node execution function by assuming that input0 is always v and input1 are always thresholds

[Integration] Interface of execute_custom_node.py to onnx_exec.py finished and first draft of unit test added