map_dtc is unreasonably slow when .f returns data.table #78
Description
When the function in map_dtc returns a data.table with many rows, map_dtc appears to be slower than it needs to be by a factor of about 100.
system.time(mlr3misc::map_dtc(1:3, function(x) runif(1e6, max = x)))
#> user system elapsed
#> 0.043 0.000 0.044
system.time(mlr3misc::map_dtc(1:3, function(x) data.table(x = runif(1e6, max = x))))
#> user system elapsed
#> 5.124 0.006 5.147 profvis tells me this this is because name_dots is called in data.table.