Auto detect main methods inherited from Java sources (including JEP 512 ones)

[Gedochao]

Follow-up to #4418 (comment)

This enables auto-detection of main methods inherited from Java classes/interfaces. Including ones added by JEP 512.

// C.java
public abstract class C {
    void main() {
        System.out.println("Hello from an instance main");
    }
}

// A.java
public class A extends C

Checklist

• tested the solution locally and it works
• ran the code formatter (scala-cli fmt .)
• ran scalafix (./mill -i __.fix)

How much have your relied on LLM-based tools in this contribution?

extensively

How was the solution tested?

added automated tests