[FIR] Preserve enhanced mutability when nullability was enhanced for warning

#KT-56989

compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/misc/mutabilityAndNullabilityForWarning.fir.kt

@@ -0,0 +1,27 @@
+// NULLABILITY_ANNOTATIONS: @org.jetbrains.annotations:warn
+// DIAGNOSTICS: -UNUSED_PARAMETER
+
+// FILE: ReadOnly.java
+package org.jetbrains.annotations;
+
+public @interface ReadOnly {}
+
+// FILE: J.java
+import java.util.List;
+import org.jetbrains.annotations.Nullable;
+import org.jetbrains.annotations.ReadOnly;
+
+public class J {
+    @ReadOnly
+    @Nullable
+    public static List<String> foo() {
+        return null;
+    }
+}
+
+// FILE: main.kt
+fun main() {
+    takeMutable(<!ARGUMENT_TYPE_MISMATCH!>J.foo()<!>)
+}
+
+fun takeMutable(l: MutableList<String>) {}

compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/misc/mutabilityAndNullabilityForWarning.kt

@@ -0,0 +1,27 @@
+// NULLABILITY_ANNOTATIONS: @org.jetbrains.annotations:warn
+// DIAGNOSTICS: -UNUSED_PARAMETER
+
+// FILE: ReadOnly.java
+package org.jetbrains.annotations;
+
+public @interface ReadOnly {}
+
+// FILE: J.java
+import java.util.List;
+import org.jetbrains.annotations.Nullable;
+import org.jetbrains.annotations.ReadOnly;
+
+public class J {
+    @ReadOnly
+    @Nullable
+    public static List<String> foo() {
+        return null;
+    }
+}
+
+// FILE: main.kt
+fun main() {
+    takeMutable(<!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>J.foo()<!>)
+}
+
+fun takeMutable(l: MutableList<String>) {}