SpringBoot ConfigDataLoaders cannot have a DeferredLogFactory injected preventing their subcomponents from logging accurately

At the moment, ConfigDataLoader instances can have a Log injected into their constructor but cannot have a DeferredLogFactory injected. This means that any subcomponents created by a ConfigDataLoader have to use the loader's Log rather than one of their own.

Being able to inject a DeferredLogFactory would be useful for Spring (Cloud) Vault where its VaultConfigDataLoader creates LeaseAwareVaultPropertySource instances that perform some logging.