several crates needs few changes (patch) to work easily in ports tree, or might
build bundled versions of libraries instead of using ports tree.
but in some cases, it's simpler to let porters manage that themselves.
the diff replaces MODCARGO_CRATES_SQLITE3_BUNDLED (specific knob for
libsqlite3-sys) by MODCARGO_CRATES_KEEP (a list of crates to keep unmodified).
adapt security/vaultwarden and www/nextcloud_notify_push to use
MODCARGO_CRATES_KEEP instead of MODCARGO_CRATES_SQLITE3_BUNDLED.
ok landry@
dffd163a87