Use sort_c after ls, so RC methods have consistent order

[d-sci]

Completes #1077, also for Reference Classes. There was the exact same issue, but it was less obvious because it was due to ls rather than sort.

Concrete minimal example (when I originally prepared this I thought it was an RStudio build pane quirk, until I saw #1077):

#' @title Case Sensitivity Test
#' @description
#' When you run [devtools::document()] in the R console, the ordering of RC
#' methods is case insensitive. When you run documentation in the build pane
#' (e.g. via `Ctrl+Shift+D`), the ordering is case sensitive.
#' @export CaseSensitivity
#' @export
CaseSensitivity <- setRefClass("CaseSensitivity",
  methods = list(
    aa = function(){
      'If case insensitive, aa will come before AZ'
      return("insensitive")
    },
    AZ = function(){
      'If case sensitive, AZ will come before aa'
      return("sensitive")
    }
  ))

would lead to:

[hadley]

How about just using sort_c() here? That makes it very clear that the results are sorted.

[d-sci]

Makes sense! Updated

[hadley]

Thanks!