Add a new `DeferredLogFactory` interface and `DeferredLogs`
implementation that can be used when a `DeferredLog` instance is needed
but the `switchOver` method should be handled elsewhere.
This interface has primarily been added so `EnvironmentPostProcessor`
classes will no longer need to implement `ApplicationEventListener`
just to switch over their logs.
Closes gh-22496
039fbdfa7c