cosigned: add version to cosigned

[cpanato]

Summary

cosigned was the last tool to expose the version/gitstate/buid time information

adding this when cosigned start, if there is another better way to expose this info please let me know

$ ./cosigned
2021/12/05 16:58:46 {
  "GitVersion": "v99.999.00-keyless-37-ge233ce8-dirty",
  "GitCommit": "e233ce828a70491d5fec699477fb2b679efce8dc",
  "GitTreeState": "dirty",
  "BuildDate": "'2021-12-04T13:38:20Z'",
  "GoVersion": "go1.17.4",
  "Compiler": "gc",
  "Platform": "darwin/amd64"
}
2021/12/05 16:58:46 Registering 2 clients
2021/12/05 16:58:46 Registering 2 informer factories
2021/12/05 16:58:46 Registering 3 informers
2021/12/05 16:58:46 Registering 3 controllers
{"severity":"INFO","timestamp":"2021-12-05T16:58:46.706712+01:00","caller":"logging/config.go:116","message":"Successfully created the logger."}
{"severity":"INFO","timestamp":"2021-12-05T16:58:46.706775+01:00","caller":"logging/config.go:117","message":"Logging level set to: info"}
{"severity":"INFO","timestamp":"2021-12-05T16:58:46.706791+01:00","caller":"logging/config.go:79","message":"Fetch GitHub commit ID from kodata failed","error":"\"KO_DATA_PATH\" does not exist or is empty"}
{"severity":"INFO","timestamp":"2021-12-05T16:58:46.706818+01:00","logger":"cosigned","caller":"profiling/server.go:64","message":"Profiling enabled: false"}

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