Splits n_reps replications among n_cores processes so that every process
gets the same base share and the remainder is handed out one replication at
a time, starting with the first process. This is the load-balancing step of
the general parallel simulation algorithm.
Examples
split_reps(1000003, 8)
#> [1] 125001 125001 125001 125000 125000 125000 125000 125000
sum(split_reps(1000003, 8))
#> [1] 1000003