Set correct IR origins for inc/dec operations

NB: in order to produce correct IR origins, the source element kinds for
some FIR elements has been changed. As a side effect, mapping PSI to FIR
slightly changed: namely, for `a[b]++`, `a[b]` used to be mapped on
`set` call or callable reference, but now it is mapped on `get` call.

^KT-61891: Fixed
^KT-64387: Fixed

compiler/fir/tree/src/org/jetbrains/kotlin/fir/FirGeneration.kt

@@ -96,8 +96,7 @@ fun generateExplicitReceiverTemporaryVariable(
                 }
             ).also { property ->
                 // Change the expression from x.a to <receiver>.a
-                val newReceiverAccess =
-                    property.toQualifiedAccess(fakeSource = receiver.source?.fakeElement(KtFakeSourceElementKind.DesugaredIncrementOrDecrement))
+                val newReceiverAccess = property.toQualifiedAccess(fakeSource = receiver.source)
 
                 if (expression.explicitReceiver == expression.dispatchReceiver) {
                     expression.replaceDispatchReceiver(newReceiverAccess)