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

analysis/low-level-api-fir/testData/getOrBuildFir/calls/setOperatorScript.txt

@@ -1,9 +1,9 @@
 KT element: KtArrayAccessExpression
-FIR element: FirResolvedNamedReferenceImpl
-FIR source kind: KtRealSourceElementKind
+FIR element: FirFunctionCallImpl
+FIR source kind: DesugaredPostfixInc
 
 FIR element rendered:
-R|test/B.set|
+R|<local>/<array>|.R|test/B.get|(R|<local>/<index_0>|)
 
 FIR FILE:
 FILE: [ResolvedTo(IMPORTS)] setOperatorScript.kts