Process default arguments in array convention calls

#KT-16520 Fixed

compiler/testData/codegen/box/defaultArguments/convention/kt16520.kt

@@ -0,0 +1,17 @@
+// IGNORE_BACKEND_FIR: JVM_IR
+var result = "fail"
+
+class A {
+    operator fun set(
+        i1: Int,
+        i2: Int = 1,
+        v: String
+    ) {
+        result = "" + i1 + i2 + v
+    }
+}
+
+fun box(): String {
+    A()[1] = "OK"
+    return if (result != "11OK") "fail: $result" else "OK"
+}