1. if an argument of a `pop` cannot be removed, then all other potential
arguments of that `pop` can't be removed either, and the same applies
to other `pop`s that touch them;
2. the same is true for primitive conversions, but this is even trickier
to implement correctly, so I simply did the same thing as with
boxing operators: replace the conversion itself with a `pop` and keep
the argument as-is.
Somehow this actually removes *more* redundant primitive type conversions
than the old code in a couple bytecode text tests, so I've patched them
to kind of use the value, forcing the instructions to stay.
#KT-46921 Fixed