Android Gradle Update & Modernization

[orelvis15]

Summary

This PR updates and modernizes the Android build configuration for libzt, improving compatibility with recent Android SDKs and Gradle versions.

✨ Changes

✅ Gradle & AGP Upgrade

• Upgraded Android Gradle Plugin from 7.3.1 → 8.1.0
• Updated Gradle wrapper from 7.5.1 → 8.4

📦 Android SDK Configuration

• compileSdk and targetSdk updated to 33 → 36
• minSdk defined explicitly as 21

🛠️ API Modernization

• Replaced deprecated:

  android.libraryVariants.all { variant -> ... }

  with:

  android.libraryVariants.configureEach { variant -> ... }

🧹 Cleanup Task

• Modernized clean task definition to use tasks.register(...) instead of legacy task(type: Delete)

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