covr::package_coverage does not pass outDir correctly to testInstalledPackage

[MLopez-Ibanez]

package_coverage creates out_dir without checking whether this is an option passed via ..... As a result, there is no way to override outDir to save the output of testing without changing install_path and that doesn't work (#517).

https://github.com/r-lib/covr/blob/84836b3f2267d861b4110570e221dd7a418a9787/R/covr.R#L482-L488