[java-dfa] Avoid marking annotation method results as non-null

While annotation implementations created by reflection never return nulls, it's possible to create a custom annotation interface implementation and nothing stops from returning null in this case. This leads to false-positives.
Fixes IDEA-269686 Wrong inspection message for nullable return value of annotation
Rollback IDEA-151174 Annotation method return values are non-nullable

GitOrigin-RevId: 88301bd8f5fb69e1e78efc23ecc1416c7c441473

java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/DfaPsiUtil.java

@@ -84,7 +84,7 @@ public final class DfaPsiUtil {
       return Nullability.UNKNOWN;
     }
 
-    if (owner instanceof PsiEnumConstant || PsiUtil.isAnnotationMethod(owner)) {
+    if (owner instanceof PsiEnumConstant) {
       return Nullability.NOT_NULL;
     }
     if (owner instanceof PsiMethod && isEnumPredefinedMethod((PsiMethod)owner)) {

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/simplifyBooleanExpressionFix/afterAnnotationMethod.java

@@ -1,8 +0,0 @@
-// "Simplify 'my.value() == null' to false" "true"
-class Test {
-  void some(SuppressWarnings my) {
-    if (my == null) {
-      System.out.println("null");
-    }
-  }
-}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/simplifyBooleanExpressionFix/beforeAnnotationMethod.java

@@ -1,4 +1,4 @@
-// "Simplify 'my.value() == null' to false" "true"
+// "Simplify 'my.value() == null' to false" "false"
 class Test {
   void some(SuppressWarnings my) {
     if (my == null || my.value() =<caret>= null) {

java/java-tests/testData/inspection/dataFlow/fixture/AnnotationMethodNotNull.java

@@ -4,7 +4,7 @@ class Test {
   }
 
   static void baz(FooBar annotation) {
-    if (<warning descr="Condition 'annotation.x() == null' is always 'false'">annotation.x() == null</warning>) {
+    if (annotation.x() == null) {
       System.out.println("null");
     }
   }