Spring boot 4 comparisons

[edeandrea]

• Update config.springboot.version to config.springboot3.version.
• Rename related native build options and CLI parameters to emphasize Spring Boot 3.x usage.
• Adjust scripts to reflect the updated naming structure across perf-lab workflow.

Fixes #74

[edeandrea]

I can get jvm & jvm-aot to work for spring boot 4, but I'm having issues with native. See spring-projects/spring-boot#48365 & oracle/graalvm-reachability-metadata#830

[edeandrea]

@holly-cummins this also 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"
    }
  }
}