SUNSET dependencies that can/should be eliminated

Opening this issue to keep track of dependencies that might cause problems at some point or may no longer be needed.

R Packages:

• PCICt: Code incorporated into startR, possibly temporarily. Archived from CRAN.
• pryr: superseded, no longer maintained. At a quick glance I could only find a commented call to the mem_used() function here: https://gitlab.earth.bsc.es/es/sunset/-/blob/master/example_scripts/test_GRIB.R#L25. However there could be more uses.