Archive OnionPerf analysis .json files

Onionperf produces two output file formats: .tpf and .json files. So far we have been archiving only the first format, but now that metrics-lib supports parsing .json files (#34070 (moved)) we can archive the second format as well. In the near future we'll want OnionPerf to stop producing .tpf files and CollecTor to stop archiving them.

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