writer-json-sarif should divide the results based on the tools that detected them

[kdudka]

The SARIF writer of csdiff should divide the results based on the tools that detected them, respecting the native structure of the SARIF data format. I believe this will ease integration of OpenScanHub with Defect Dojo.

[kdudka]

This is no longer needed for DefectDojo. #147 addressed the issue in a much easier and backward-compatible way.