Similarly to 742fef9042 with OperationsMapGenerated, use optimized
`when` over strings instead of lambdas because lambdas lead to a lot of
bytecode.
The change in `IrConst.toPrimitive` is needed because for operations
like `Byte.plus(Int)` the IrConst instance would have the IR type for
kotlin.Byte, but the actual runtime value of type Int
(java.lang.Integer), which would lead to CCE from
`interpretBinaryFunction`. Previously it didn't fail because of
unchecked cast before calling the lambda, which allowed a value of
runtime type java.lang.Integer to sneak through to the lambda parameter
and be "unboxed" to the correct type via the `(... as Number).toByte()`
conversion which backend generates.
The main benefit of this change is that it reduces the size of the
proguarded compiler jar by ~0.69%.
Alexander Udalov