/usr/lib/mono/2.0/I18N.West.dll is in libmono-i18n-west2.0-cil 2.10.8.1-1ubuntu2.3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/mono/2.0/../gac/I18N.West/2.0.0.0__0738eb9f132ed756/I18N.West.dll