[Code Gen] Added template for single node code generation and deleted redundant lines in example cpp file

[Test] Added call of hls library in .cpp file and created a shell script with the compile command (should only stay during dev->delete later)

[Test] Changed execute_custom_node.py and test cpp file to check if passing arrays via .npy files works

[Test] Omit removing of the temporary file which contains the input values and created a .cpp for testing the single node execution

[Execution] Added if tree to read out the attribute backend to enable the path for executing of hls lib custom nodes