[FIR] Introduce containsMultipleNonSubsumed to intersection overrides

After this change the IO created for
`SimpleColoredComponent::setToolTipText`
will be `containsMultipleNonSubsumed == true`
while IOs created for classes in
`intersectionOverridesIntersection.kt`
will have this property set to `false`.

^KT-65972 Fixed

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

@@ -334,7 +334,10 @@ class FirSignatureEnhancement(
                     this.name = name!!
                     status = firMethod.status
                     symbol = if (isIntersectionOverride) {
-                        FirIntersectionOverrideFunctionSymbol(methodId, overriddenMembers.map { it.symbol })
+                        FirIntersectionOverrideFunctionSymbol(
+                            methodId, overriddenMembers.map { it.symbol },
+                            containsMultipleNonSubsumed = (firMethod.symbol as? FirIntersectionCallableSymbol)?.containsMultipleNonSubsumed == true,
+                        )
                     } else {
                         FirNamedFunctionSymbol(methodId)
                     }.also { functionSymbol = it }

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

@@ -375,7 +375,11 @@ class JavaOverrideChecker internal constructor(
         extractedOverrides: Collection<MemberWithBaseScope<D>>,
         dispatchClassSymbol: FirRegularClassSymbol?,
     ): Visibility {
-        val overridesWithoutIntersections = extractedOverrides.flatMap { it.flattenIntersectionsRecursively() }
+        // It's crucial that we only unwrap phantom intersection overrides.
+        // See comments in the following tests for explanation:
+        // - intersectionWithMultipleDefaultsInJavaOverriddenByIntersectionInKotlin.kt
+        // - intersectionOverridesIntersection.kt
+        val overridesWithoutIntersections = extractedOverrides.flatMap { it.flattenPhantomIntersectionsRecursively() }
         val nonSubsumed = overridesWithoutIntersections.nonSubsumed().filterOutDuplicates()
 
         // In Java it's OK to inherit multiple implementations of the same function