Fix input file name display in benchmark_contract function

[Galoretka]

Previously, the benchmark_contract function used the input_file variable, which was not defined within the function scope, leading to incorrect or empty file names in the benchmark output table.
This commit ensures that input_file is correctly set to the basename of the input path inside the function, so the results table now accurately displays the contract file name for each benchmarked contract.

[github-actions]

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