Level of CFGNode is used to determine which call is a common one for
creating node with union of arguments (to merge flow from multiple
in-place lambdas). Before this change calls in different when branches
may have same node level, which entail passing smartcasts from moddle of
one branch to another
```
val x: Any = ...
when {
... -> run { x as String } // (1)
... -> {
run {
x.foo()
} // (2)
"hello"
}
}
```
Call `(1)` was assumed as argument of call `(2)` which is incorrect
#KT-44814 Fixed
Dmitriy Novozhilov