Login Flow revisions

[LossyDragon]

Description

Just some revisions that I'm tracking to help Kotlin, and mobile development.

Changes so far:
Added exceptions that could be thrown for login flow
Added examples in Kotlin for standard and QR login flows
Fixed: pollingWaitForResult() can be cancelled in Kotlin (Coroutines). Cancellation is not possible in Java, so a compat method was added for compatibility. For Java it will just block until the async job fails it.
Fixed interface package name for handing Service Methods.

Checklist

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

[LossyDragon]

So far I haven't encountered any major issues with this PR, after some time.

Some minor issues I'd like to correct before merging this revision:

• Kotlin 1.9.0 / Gradle 8.2.1 are stable as of this post
• kotlinOptions deprecated in gradle files
• Signing in with a SteamGuard account in an android app won't show it's session info in the offical steam app. But the samples work fine(?!). (The "Steam App" session show's the same error, but I would expect that since it's contains your SG stuff, so you don't lock yourself out)

[LossyDragon]

Still can't figure out the last bullet point above as it works when using it as a standard JVM app. But its a non blocking issue.