Minor, annotate visibility constants with NotNull

To avoid nullability warnings on ClassDescriptor#getVisibility and
implementations

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/JavaVisibilities.java

@@ -26,6 +26,7 @@ public class JavaVisibilities {
     private JavaVisibilities() {
     }
 
+    @NotNull
     public static final Visibility PACKAGE_VISIBILITY = new Visibility("package", false) {
         @Override
         public boolean isVisible(@Nullable ReceiverValue receiver, @NotNull DeclarationDescriptorWithVisibility what, @NotNull DeclarationDescriptor from) {
@@ -63,6 +64,7 @@ public class JavaVisibilities {
         }
     };
 
+    @NotNull
     public static final Visibility PROTECTED_STATIC_VISIBILITY = new Visibility("protected_static", true) {
         @Override
         public boolean isVisible(@Nullable ReceiverValue receiver, @NotNull DeclarationDescriptorWithVisibility what, @NotNull DeclarationDescriptor from) {
@@ -87,6 +89,7 @@ public class JavaVisibilities {
         }
     };
 
+    @NotNull
     public static final Visibility PROTECTED_AND_PACKAGE = new Visibility("protected_and_package", true) {
         @Override
         public boolean isVisible(@Nullable ReceiverValue receiver, @NotNull DeclarationDescriptorWithVisibility what, @NotNull DeclarationDescriptor from) {

core/descriptors/src/org/jetbrains/kotlin/descriptors/Visibilities.java

@@ -32,6 +32,7 @@ import org.jetbrains.kotlin.utils.CollectionsKt;
 import java.util.*;
 
 public class Visibilities {
+    @NotNull
     public static final Visibility PRIVATE = new Visibility("private", false) {
         @Override
         public boolean mustCheckInImports() {
@@ -104,6 +105,7 @@ public class Visibilities {
      *      }
      *  }
      */
+    @NotNull
     public static final Visibility PRIVATE_TO_THIS = new Visibility("private_to_this", false) {
         @Override
         public boolean isVisible(@Nullable ReceiverValue thisObject, @NotNull DeclarationDescriptorWithVisibility what, @NotNull DeclarationDescriptor from) {
@@ -133,6 +135,7 @@ public class Visibilities {
         }
     };
 
+    @NotNull
     public static final Visibility PROTECTED = new Visibility("protected", true) {
         @Override
         public boolean mustCheckInImports() {
@@ -198,6 +201,7 @@ public class Visibilities {
         }
     };
 
+    @NotNull
     public static final Visibility INTERNAL = new Visibility("internal", false) {
         @Override
         public boolean mustCheckInImports() {
@@ -213,6 +217,7 @@ public class Visibilities {
         }
     };
 
+    @NotNull
     public static final Visibility PUBLIC = new Visibility("public", true) {
         @Override
         public boolean mustCheckInImports() {
@@ -225,6 +230,7 @@ public class Visibilities {
         }
     };
 
+    @NotNull
     public static final Visibility LOCAL = new Visibility("local", false) {
         @Override
         public boolean mustCheckInImports() {
@@ -237,6 +243,7 @@ public class Visibilities {
         }
     };
 
+    @NotNull
     public static final Visibility INHERITED = new Visibility("inherited", false) {
         @Override
         public boolean mustCheckInImports() {
@@ -250,6 +257,7 @@ public class Visibilities {
     };
 
     /* Visibility for fake override invisible members (they are created for better error reporting) */
+    @NotNull
     public static final Visibility INVISIBLE_FAKE = new Visibility("invisible_fake", false) {
         @Override
         public boolean mustCheckInImports() {
@@ -264,6 +272,7 @@ public class Visibilities {
 
     // Currently used as default visibility of FunctionDescriptor
     // It's needed to prevent NPE when requesting non-nullable visibility of descriptor before `initialize` has been called
+    @NotNull
     public static final Visibility UNKNOWN = new Visibility("unknown", false) {
         @Override
         public boolean mustCheckInImports() {