Previously `getIrFunctionSymbol` effectively did the same thing as `getOrCreateIrFunction`,
but in a slightly different way. To avoid logic duplication and source of
potential inconsistencies, implementation was changed to just delegate to
`getOrCreateIrFunction`
Changes in `computeIrOrigin` were required because origin for callables in
`getOrCreateIrFunction` and `getIrFunctionSymbol` was computed differently,
so `computeIrOrigin` was changed to preserve existing behavior
^KT-60924
Dmitriy Novozhilov
bb093037c0