Support KSP (Kotlin Symbol Processing)

Currently ObjectBox supports using KAPT for processing annotations in Kotlin.
KSP is a new Kotlin annotation processing framework by Google and supported by Jetbrains that processes annotations in a far more 'native' way than KAPT, resulting in improved performance and an API more suited for Kotlin. Consequently, KAPT has lost its focus from the Kotlin team (source).
ObjectBox should seriously consider providing an implementation for processing annotations in Kotlin using KSP. For reference, see this recent build time analysis:

A whopping 75.8% (24.2 seconds) of build time is spent on generating KAPT stubs, which supposedly KSP avoids completely. On the other hand, it appears only 0.8 seconds is spent doing actual Objectbox work.

Further reading:
What is KSP?
Why KSP?
KSP Github

この issue では、リポジトリのファイル、テスト、エントリポイントは指定されていません。まずリンク先の KSP ドキュメントと既存の KAPT 統合を調査し、そのうえで、KSP を介した同等の ObjectBox アノテーション処理を実現し、ビルド時の動作と生成コードの動作を検証することを完了条件として定義してください。