Remove resampleWrapper(): exported, uncalled, and broken since before 2014 #1518

resampleWrapper() is exported but cannot run, and nothing in the package calls it.

library(caret)
df <- data.frame(a = rnorm(20), b = rnorm(20), .outcome = rnorm(20))
x <- list(data = df, method = getModelInfo("lm", regex = FALSE)[[1]])
caret:::resampleWrapper(x, 1:15)
#> Error in do.call(createModel, x) : argument "x" is missing, with no default

The body builds its argument list around x$data:

resampleWrapper <- function(x, ind) {
  out <- rep(NA, dim(x$data)[1])
  trainData <- x$data
  x$data <- x$data[ind, ]
  tmpModelFit <- do.call(createModel, x)
  ...
}

That matches a createModel(data = ...) signature which does not exist in this repository's history: at the first commit (caret 6.0-30, 2014) pkg/caret/R/createModel.R already defined createModel2(x, y, wts, method, tuneValue, obsLevels, pp, last, classProbs, ...). So data lands in ... while x and y are never supplied.

grep -rn resampleWrapper R/ finds only the definition and the @aliases line in createModel.Rd; the only other reference is export(resampleWrapper) in NAMESPACE.

Since it is exported, it is grouped with the other dead exports for removal after a reverse-dependency check (as was done for predict.PLS() in #1512). Nothing can be calling it successfully, but the export is public API.

Found while raising test coverage: it is the only file left at 0%, and there is nothing meaningful to test.