Currently only the default GHC (8.10.7) is added to packages.json,
leading e. g. repology to believe we don't ship an up to date GHC which
is inaccurate.
Now simply inherits attrsets from super directly instead of mapping getAttr over
a list of strings.
Filtering isn't really needed as non-existent subsets should just be removed
from this list when removing them from Nixpkgs (such an action warrants a
tree-wide search which should come across this file).
recurseIntoAttrs can simply be mapAttr'd now.
Some subsets have been removed because they no longer exist.
Sorted the list while I was at it.
