Draft: [Add][WIP] benchmark scripts

python benchmarks/generate_graph.py --operator-config benchmarks/operator_config/add_config.json --ref benchmarks/results/add_onnxruntime.json --libs benchmarks/results/add_torch.json benchmarks/results/add_aidge_backend_cpu.json

{
    "library": "aidge_backend_cpu",
    "compare": {},
    "time": {
        "dim size": {
            "1": [
                1.1659999999968917e-05,   // <- one iteration time measured
                ...
             ],
            "4": [...],
            "16": [...],
            "64": [...],
            "128": [...]
        },
        "one dim broadcasted (idx)": {
            ...
        },
        "two dims broadcasted (idx)": {
            ...
        },
        "nb missing axis 1st input": {
            ...
        }
    }
}

{
    "operator": "Add",
    "opset_version": 21,
    "initializer_rank": 2,
    "base_configuration": {
        "input_shapes": [
	    ["input_0", [64, 64, 64, 64]],
	    ["input_1", [64, 64, 64, 64]]
	],
	    "attributes": {}
    },
    "test_configuration": {
        "main_parameters": {
	    "dim size": [
		1,4,16,64,128
	    ],
            "one dim broadcasted (idx)": [...],
            "two dims broadcasted (idx)": [...],
            "nb missing axis 1st input": [...]
	},
        "other_parameters": {
	    "dim size": {
                "1": {
		    "attributes": {},
		    "input_shapes": [
			["input_0", [1, 1, 1, 1]],
                        ["input_1", [1, 1, 1, 1]]
		    ]
		},
		"4": {
		    "attributes": {},
		    "input_shapes": [
			["input_0", [4, 4, 4, 4]],
                        ["input_1", [4, 4, 4, 4]]
		    ]
		},
...