FIR: Ensure that the array set argument (on RHS of =) is always mapped

to the last parameter of the set operator function, even if there are
missing or too many index arguments.

compiler/testData/diagnostics/tests/checkArguments/arrayAccessSetTooManyArgs.fir.kt

@@ -0,0 +1,10 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+class A {
+    operator fun get(x: Int) {}
+    operator fun set(x: String, value: Int) {}
+
+    fun d(x: Int) {
+        this["", <!TOO_MANY_ARGUMENTS!>1<!>] = 1
+    }
+}