Reconsider R Package Scan button

[kgartland-rstudio]

We ended up removing the R Package Scan button due to this bug:

#2403

Further discussion here:
https://positpbc.slack.com/archives/C05D7NZD52S/p1729259573066909

It would be nice to have a button that configures renv for users but the original implementation seemed to only add functionality if the user already had an renv/activate.R with either no renv.lock or a renv.lock file with missing or mismatched packages to the renv/library. Most real R users won't get into this scenario so the Scan button didn't offer much value.

Aron provided some prior art around renv management in the rsconnect package:
https://github.com/rstudio/rsconnect/blob/2fe8fdef45f843cfb1316fecb443ac30a0ed8a42/R/bundlePackageRenv.R#L1-L33