Move Suggest-ed package tests out of tests.Rraw

To reduce RAM usage in attempt to work on (I guess severely overloaded) CRAN Windows #5507 
Thanks to a comment by @ben-schwen here: https://github.com/Rdatatable/data.table/pull/5515#issuecomment-1307133538