#3385 Warn when mapper-declared lifecycle methods are never used - #4114

Unused @BeforeMapping / @AfterMapping methods currently produce no diagnostic.
If a developer adds an extra parameter by mistake, the method is silently ignored.

For the mapper from the issue:

@Mapper
public interface X {

    B map(A a);

    @AfterMapping
    default void good(A a) {
    }

    @AfterMapping
    default void nowarning(String break_it, A a) {
    }
}

good is invoked, but nowarning is not, and MapStruct does not warn.

Change

Warn only for lifecycle methods that are declared directly on the processed mapper and never type-match any generated mapping method.

Out of scope on purpose, so existing overload / inheritance patterns stay quiet:

• methods inherited from a super type (BaseMapper)
• methods coming from Mapper#uses
• overloads that match by type but are dropped in favor of a more specific one

CarMapper.neverMatched(...) is the remaining true unused case and now expects the warning.

Verification

Run from the repository root with JDK 21.

• Issue3385Test covers unused @AfterMapping and @BeforeMapping
• CallbackMethodTest, CallbackMethodTypeMatchingTest, Issue3849Test stay green
• ./mvnw -pl processor test -Dtest=Issue3385Test,CallbackMethodTest,CallbackMethodTypeMatchingTest,Issue3849Test

Fixes #3385