Change publishDir for alevin output to be different from publishDir for rds files

[allyhawkins]

In an effort to keep the file organization close to how the final product will look, we want to keep the alevin output directories separate from the directories that are holding the final filtered and unfiltered rds files. To do this we will want to alter the publishDir to be different between the map_quant_rna workflow and the generate_rds process. For now we still want to keep the alevin directories and store them (without the RAD files), so will just move them to a new place rather than removing the publishDir step completely.