Make vec_ptype_common() use list2()

[DavisVaughan]

Again avoiding the allocation of rlang_env_dots_list()

pkgs <- tibble::tribble(
  ~vctrs             , ~rlang        ,
  "vctrs"            , "rlang"       ,
  "r-lib/vctrs#2071" , "r-lib/rlang" ,
)

cross::bench_versions(pkgs = pkgs, {
  library(vctrs)
  x <- as.list(1:1e6)
  bench::mark(vec_ptype_common(!!!x))
})
#> # A tibble: 2 × 7
#>   pkg                      expression    min median `itr/sec` mem_alloc `gc/sec`
#>   <chr>                    <bch:expr> <bch:> <bch:>     <dbl> <bch:byt>    <dbl>
#> 1 vctrs, rlang             vec_ptype… 39.4ms 39.9ms      25.1    7.63MB     4.56
#> 2 r-lib/vctrs#2071, r-lib… vec_ptype… 23.9ms 24.3ms      41.1    3.27KB     0

# When a `ptype` is passed through
cross::bench_versions(pkgs = pkgs, {
  library(vctrs)
  x <- as.list(1:1e6)
  bench::mark(vec_ptype_common(!!!x, .ptype = integer()))
})
#> # A tibble: 2 × 7
#>   pkg                      expression    min median `itr/sec` mem_alloc `gc/sec`
#>   <chr>                    <bch:expr> <bch:> <bch:>     <dbl> <bch:byt>    <dbl>
#> 1 vctrs, rlang             vec_ptype… 4.87ms 5.09ms      185.    7.63MB     43.7
#> 2 r-lib/vctrs#2071, r-lib… vec_ptype… 1.07µs 1.19µs   694085.    3.06KB      0

^{Created on 2025-10-18 with reprex v2.1.1}