last_trace() advice not helpful when missing {crayon} [aka odd mix of {crayon} & {cli}]

[MichaelChirico]

I got an error and saw the expected advice:

Error in `FUN()`:
! `arg` must be a symbol
Run `rlang::last_trace()` to see where the error occurred.

However, the current environment doesn't have {crayon}, so that advice turned out to be less than helpful:

rlang::last_trace()
# Error in loadNamespace(x) : there is no package called ‘crayon’

I peeked around and AFAICT ultimately this is the issue:

rlang/R/utils.R

Lines 165 to 166 in 7371bac

	if (cli::num_ansi_colors() >= 256) {
	crayon::make_style(grDevices::grey(0.6), colors = 256)(x)

I see three options:

1. Use {cli} completely and avoid {crayon}
2. Don't give the unhelpful advice if {crayon} is missing
3. Add a check_installed("crayon") branch in style_dim_soft().

This last is very easy and I'll file a quick PR, but I wonder if the others will be worth the higher investment.