feat: use ISO 8601 with millisecond precision as timestamp format
We were using RFC3339, which was Logrus' and LabKit's default. LabKit was bumped from v1.9.0 to v1.10.0 in the process.
We were using RFC3339, which was Logrus' and LabKit's default. LabKit was bumped from v1.9.0 to v1.10.0 in the process.