Migrates from the deprecated toCommandLineShell to toCommandLineShellGNU.
This changes the output format to use GNU-style concatenated options
(--line-height=28) and adds shell escaping for values with special
characters (e.g., '#1e1e2e' becomes '--ab=#1e1e2e'). The format
was verified to work correctly with bemenu.
Signed-off-by: Austin Horstman <khaneliman12@gmail.com>
Instead of having to manually stub packages that should not be
downloaded we instead automatically stub all packages (except a small
list of whitelisted ones). Tests can re-introduce the real package by
using the `realPkgs` module argument.
