Instruct which benchmarks to run through the API

[Elexy]

This pulls out more of the configuration to the API.
You can specify which benchmarks to run and if ALL the clinic tools should be run on each of them.

curl -XPOST -d '{"commit":"", "clinic": { "enabled": false },  "benchmarks": { "tests": ["localTransfer_tcp_mplex", "unixFsAdd"]}}' -H "Content-Type: application/json" -H "x-ipfs-benchmarks-api-key: supersecret" -k http://localhost:9000