Steamclient updates

[LossyDragon]

Description

• Port the steamclient package classes to kotlin, maintaining java compatibility of course.
• [SteamClient] Use kotlin Channels for callbackQueue
• [SteamClient] Remove freeLastCallback and getAllCallbacks.
• [SteamClient] Calling getCallback and waitForCallback now always removes a callback, there is no more peek and freelast.
• [SteamClient] Add SteamAuthentication to SteamClient, SteamAuthentication will get its own instance of UnifiedMessages.
• [SampleLogonAuthentication] Update with new login method (above) and more notes on how to login, configuration, and retain login persistence.
• Update tests.
• AuthPollResult#newGuardData can be nullable.
• SteamAuthentication will now reference the Unified hander on its own.

Checklist

• [x] Code compiles correctly
• [x] All tests passing
• [x] Samples run successfully
• [x] Extended the README / documentation, if necessary

[LossyDragon]

Tested changes on a seperate java and android project, working ok.

[LossyDragon]

This also checks off PR 1397 on #181