access: add a more generic "default" access policy script

src/config-split/main.lua.d/20-default-access.lua

src/config-split/main.lua.d/50-default-access-config.lua

src/config-split/main.lua.d/90-enable-all.lua

src/config/config.lua.d/20-default-access.lua

src/config/config.lua.d/90-access-flatpak.lua

src/scripts/access/access-default.lua

src/scripts/access/access-flatpak.lua