Resolve #3245865 "Enable retain original"

Adding a field_defaults.install file seemed to help, and "Retain original entity updated time" is now enabled by default after installing the module, but it can still be disabled by the user.

I also updated field_defaults.configuration to field_defaults.settings a few places, so now there's only a single field_defaults.settings when you run drush config:get, which seemed necessary. I hope I didn't break something elsewhere in the module.