[FIR] Fix arguments mapping for indexed set operator

Now processPositionArgument changes STATE as well as processNamedArgument

^KT-59386

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

@@ -20,16 +20,23 @@ object Z {
     }
 }
 
+object W {
+    operator fun set(vararg va: Int, value: Int) {
+    }
+}
+
 fun test() {
-    A[0] = ""
+    A[0] = <!ARGUMENT_TYPE_MISMATCH!>""<!>
     A[0] = 2.72
 
-    B[0] = ""
-    B[0] = 2.72
+    B[0] = <!ARGUMENT_TYPE_MISMATCH!>""<!>
+    B[0] = <!ARGUMENT_TYPE_MISMATCH!>2.72<!>
     B[0] = true
 
-    D[0] = ""
+    D[0] = <!ARGUMENT_TYPE_MISMATCH!>""<!>
     D[0] = 2.72
 
     Z[<!TOO_MANY_ARGUMENTS!>0<!>] = <!TOO_MANY_ARGUMENTS!>""<!>
+
+    W[0] = 1
 }