Add an extension property for storing a cached logger

Analogous to the extension function `T.logger()` which constructs a logger using the class of `T`, an extension property `T.logger` should be added for an alternative to using the `Logging` mixin. The general change is fairly simple:

```kt
inline val <reified T> T.logger: KotlinLogger
  get() = cachedLoggerOf(T::class.java)
```