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.
Alternatively, we could improve the lookup utilities and their usages to
always find the exact override of a symbol from
Collection/Iterable/CharSequence/etc, but since we need to load the
original symbol anyway in cases when the loop subject's type is a type
parameter, we might as well simplify everything and always reference the
original symbol.
Also improve exception message and removed unused declarations in
IrBackendUtils.kt.
Ivan Kylchik