[issue #2221] [issue #788] Lombok now adds nullity annotations.

Which 'flavour' is defined in lombok.config; applied to toString, equals, canEqual, and plural-form of `@Singular`.

test/transform/resource/before/BuilderSingularNullBehavior2.java

@@ -0,0 +1,11 @@
+//CONF: lombok.addNullAnnotations = checkerframework
+import java.util.List;
+
+import lombok.Singular;
+import lombok.Singular.NullCollectionBehavior;
+
+@lombok.Builder
+class BuilderSingularNullBehavior2 {
+	@Singular(nullBehavior = Singular.NullCollectionBehavior.JDK) private List<String> locations;
+	@Singular(nullBehavior = lombok.Singular.NullCollectionBehavior.IGNORE) private List<String> doohickeys;
+}