[FEATURE] Support JSpecify @NullMarked

Describe the feature Support of the JSpecify's @NullMarked annotation when generating constructors. Goal: creating class instances with all non-nullable fields set and not null after instantiation.

Lomboked version:

import org.jspecify.annotations.NullMarked;

@NullMarked
@RequiredArgsConstructor
public class Bean {

    private String s;

}

Delomboked version:

import org.jspecify.annotations.NullMarked;

@NullMarked
public class Bean {
    private String s;

    @Generated
    public Bean(String s) {
        if (s == null) {
            throw new NullPointerException("s is marked non-null but is null");
        } else {
            this.s = s;
        }
    }
}

Describe the target audience Users of JSpecify annotation.

Additional context In JSpecify specification, annotating a class with @NullMarked indicates that all its fields are not nullable (except if they are annotated with @Nullable).

However, the @NullMarked can also been applied directly on a package through its package-info.java. In that case, all classes under this package are implicitly marked @NullMarked as well and so the same constructor generation rules as above should apply.