Mark logger functions internal

[twyatt]

Overlooked these being on the public API.
Caught it when running ./gradlew apiDump in #56.

[twyatt]

Unfortunately going to abandon this change.
The logging is useful from other modules (namely keep-alive at this point).

Ideally we'd expose the internal logger functions to the keep-alive module via friend-paths but I could not find relevant documentation, and was unable to get it working through trial-and-error.

It's a minor issue to expose the logger functions on the public API. If someone has insight into the friend-paths into how to get it working then it'd be great to re-tackle this.

Referenced the following issues for my attempts at getting friend-paths working:

• KT-34901
• KT-21910
• KT-14654
• KT-24555
• KT-20760
• KT-34009