Convert spring-core tests from groovy to java

[abhisesh]

Related to #7195.

Converts spring core instrumentation tests from groovy to java.

[mateuszrzeszutek]

You'll need to add the following code snippet to build.gradle.kts to fix the failing checks:

// spring 6 requires java 17
if (findProperty("testLatestDeps") as Boolean) {
  otelJava {
    minJavaVersionSupported.set(JavaVersion.VERSION_17)
  }
}

Our latestDepTest jobs try to test the instrumentation against the most recent instrumented library version; for spring-core it's Spring 6.+, which requires Java 17 to compile and run.

[mateuszrzeszutek]

Thanks @abhisesh !