SpringBoot Make resolution algorithm of ConnectionDetailsFactory more explicit

This commit moves the resolution check for ConnectionDetailsFactory to a dedicated method to make it more clear that it is meant to verify that the implementation is resolved and can be loaded from the classpath.

The previous algorithm relied on a behavior of ResolvableType that only resolves the first level generics. Further improvements in Spring Framework 6.2 make this check invalid as some implementations use a Container that can hold a nested generic.