Fix gitlab url for subgroups

[galachad]

Another gitlab bug to fix cc: @aronatkins.

This change allow install packages from subgroups.

Example:
https://gitlab.com/main518/child/skeleton

Minimal reproduce example:

# remotes::install_gitlab("main518/child/skeleton")

library(shiny)
library(skeleton)

ui <- fluidPage(

)

server <- function(input, output) {

}

shinyApp(ui = ui, server = server)

The / needs to be replace with %2F for RemoteRepo.

> packageDescription("skeleton")
Package: skeleton
Title: A skeleton R package.
Version: 1.0.1
Author: Kevin Ushey
Description: Doesn't really do anything.
Depends: R (>= 3.0.1)
License: GPL (>= 2)
Encoding: UTF-8
LazyData: true
RemoteType: gitlab
RemoteHost: gitlab.com
RemoteRepo: child/skeleton
RemoteUsername: main518
RemoteRef: HEAD
RemoteSha: 958296dbbbf7f1d82f7f5dd1b121c7558604809f
NeedsCompilation: no
Packaged: 2023-01-09 13:25:41 UTC; forysa
Built: R 4.0.5; ; 2023-01-09 13:25:41 UTC; unix

-- File: /Library/Frameworks/R.framework/Versions/4.0/Resources/library/skeleton/Meta/package.rds 

[aronatkins]

Thanks, @galachad

Note to @toph-allen --

Per https://docs.gitlab.com/ee/api/repositories.html#get-file-archive, the :id needs to be URL-encoded. We may want to use this opportunity to escape other characters, as well.

URLencode(pkgRecord$remote_repo, TRUE)

Additionally, we should update NEWS.

[toph-allen]

Yeah, we should use URLencode here, I think.

I'm also going to check GitHub and Bitbucket to see if we should treat them similar.

We may also want to add this case to the gitlabArchiveUrl test.

Thanks for submitting this, @galachad! I may open a new branch on rstudio/packrat to make the above changes, and if I do that, I'll close this PR with a reference to that.

[aronatkins]

Replaced by #700.