Make primops for `{Int,Word}32#`

Progress towards #19026 (closed).

The type was added before, but not its primops. We follow the conventions in 36fcf9ed and 2c959a18 for names and testing.

Along with the previous 8- and 16-bit primops, this will allow us to avoid many conversions for 8-, 16-, and 32-bit sized numeric types.