Eventually we'd like to get rid of this class altogether but for now
this PR reduces the surface area by removing methods from the class and
moving classes out into their own files.

* `adapter_method` was moved into database configurations
* `initialize_dup` was removed because it was only used in tests
* Resolver is now it's own class under connection adapters
* ConnectionUrlResolver, only used by the configurations, is in a class
under DatabaseConfigurations
Co-authored-by: NJohn Crepezzi <john.crepezzi@gmail.com>