We are going to deprecate `WITH_RUNTIME` directive. The main reason
behind this change is that `WITH_STDLIB` directive better describes
its meaning, specifically it will add kotlin stdlib to test's classpath.
We can only use IrStrinConcatentation to represent calls to Any?.toString
and toString calls on primitive types. Otherwise, x.toString() and "$x"
are observably different when x is a non-null type with null value
(e.g., an @NotNull value coming from Java).