speed up `generate(type = "draw")`

As of now, the package re-computes format_params(x) in each replicate, which accounts for about half of the total evaluation time of the function.

With main dev:

library(infer)

gss_hyp <-
   gss %>%
   specify(response = sex, success = "female") %>%
   hypothesize(null = "point", p = .5)

bench::mark(
   generate = generate(gss_hyp, reps = 1000, type = "draw")
)
#> # A tibble: 1 × 6
#>   expression      min   median `itr/sec` mem_alloc `gc/sec`
#>   <bch:expr> <bch:tm> <bch:tm>     <dbl> <bch:byt>    <dbl>
#> 1 generate     58.4ms   61.7ms      15.2    42.5MB     30.4

With this PR:

#> # A tibble: 1 × 6
#>   expression      min   median `itr/sec` mem_alloc `gc/sec`
#>   <bch:expr> <bch:tm> <bch:tm>     <dbl> <bch:byt>    <dbl>
#> 1 generate     33.5ms   33.5ms      29.9    40.5MB     747.

^{Created on 2023-04-10 with reprex v2.0.2}

tidymodels / infer

speed up `generate(type = "draw")` #493