FIR Java: simplify flexible nullability manipulations

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/JavaUtils.kt

@@ -200,7 +200,7 @@ private fun ClassId.toConeFlexibleType(
     toConeKotlinType(
         typeArguments,
         isNullable = false,
-        attributes.intersectUnless(ConeAttributes.WithFlexibleNullability) { it.hasEnhancedNullability }
+        attributes.withFlexibleUnless { it.hasEnhancedNullability }
     ),
     toConeKotlinType(typeArgumentsForUpper, isNullable = true, attributes)
 )
@@ -242,7 +242,7 @@ private fun JavaClassifierType.toConeKotlinTypeWithoutEnhancement(
     else
         ConeFlexibleType(
             lowerBound.withAttributes(
-                lowerBound.attributes.intersectUnless(ConeAttributes.WithFlexibleNullability) { it.hasEnhancedNullability }
+                lowerBound.attributes.withFlexibleUnless { it.hasEnhancedNullability }
             ),
             upperBound
         )
@@ -316,7 +316,7 @@ private fun getErasedVersionOfFirstUpperBound(
                 // Avoid exponential complexity
                 ConeFlexibleType(
                     lowerBound.withAttributes(
-                        lowerBound.attributes.intersectUnless(ConeAttributes.WithFlexibleNullability) { it.hasEnhancedNullability }
+                        lowerBound.attributes.withFlexibleUnless { it.hasEnhancedNullability }
                     ),
                     lowerBound.withNullability(ConeNullability.NULLABLE)
                 )

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/enhancement/javaTypeUtils.kt

@@ -92,7 +92,7 @@ private fun ConeKotlinType.enhanceConeKotlinType(
             val lowerResult = lowerBound.enhanceInflexibleType(
                 session, TypeComponentPosition.FLEXIBLE_LOWER, qualifiers, index,
                 attributes = if (needsFlexibleNullabilityAttribute)
-                    lowerBound.attributes.intersect(ConeAttributes.WithFlexibleNullability)
+                    lowerBound.attributes.withFlexible()
                 else
                     lowerBound.attributes
             )

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/scopes/JavaClassMembersEnhancementScope.kt

@@ -106,7 +106,7 @@ class JavaClassMembersEnhancementScope(
                             if (valueParameter.returnTypeRef.coneType is ConeFlexibleType) {
                                 ConeFlexibleType(
                                     type.withAttributes(
-                                        type.attributes.intersectUnless(ConeAttributes.WithFlexibleNullability) {
+                                        type.attributes.withFlexibleUnless {
                                             it.hasEnhancedNullability
                                         }
                                     ),