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.
neomutt: Updated options and added tests
neomutt: Added test for individual mailbox type
neomutt: Formatted code
neomutt: Enable ssl_force_tls based on IMAP instead of SMTP
neomutt: Applied suggestions from @chayleaf
neomutt: fix breaking tests