Capture Spring4 metrics

[edeandrea]

See quarkusio/spring-quarkus-perf-comparison#74 & quarkusio/spring-quarkus-perf-comparison#80

This means additions to the json structure

{
  "timing": {
    "start": "2025-12-01T19:14:55Z",
    "stop": "2025-12-01T19:20:46Z"
  },
  "results": {
    "spring4-jvm": {
       // new metrics in here
    },
    "spring4-jvm-aot": {
      // new metrics in here
    },
    "spring4-native": {
      // new metrics in here
    }
  },
  "config": {
    "springboot3": {
      "native_build_options": "",
      "version": "3.5.8"
    },
    "springboot4": {
      "native_build_options": "",
      "version": "4.0.0"
    }
  }
}