Add standardize_arguments() function

[rossellhayes]

.user_code <- "mean(rnorm(10))"
standardize_arguments(.user_code)
#> [1] "mean(x = rnorm(n = 10, mean = 0, sd = 1), trim = 0, na.rm = FALSE)"
standardize_arguments(.user_code, recurse = FALSE)
#> [1] "mean(x = rnorm(10), trim = 0, na.rm = FALSE)"
standardize_arguments(.user_code, add_defaults = FALSE)
#> [1] "mean(x = rnorm(n = 10))"

^{Created on 2023-03-30 with reprex v2.0.2}