Add Kotlin 2.4.0 and AGP 9.2.1 compatibility

[Sergan2B]

Summary

• Fix Kotlin 2.4 FIR extension registration by selecting the Kotlin 2.4 adapter when the compiler exposes the new FIR registration API.
• Update the compiler project to Kotlin 2.4.0 and Gradle 9.5.1.
• Refresh generated compiler test data for Kotlin 2.4.0.
• Update sample apps to use io.insert-koin.compiler.plugin:1.0.1.
• Migrate Android playgrounds to AGP 9.2.1 built-in Kotlin and update KSP to 2.3.9.
• Document Kotlin 2.4 compatibility in README.

Verification

• ./gradlew check --stacktrace
• ./gradlew publishToMavenLocal --no-configuration-cache --stacktrace
• cd test-apps && ./gradlew :sample-app:jvmTest :sample-app:jvmRun --stacktrace
• cd playground-apps/app-dsl && ANDROID_HOME=/Users/User/Library/Android/sdk ./gradlew :app:assembleDebug --stacktrace
• cd playground-apps/app-annotations && ANDROID_HOME=/Users/User/Library/Android/sdk ./gradlew :app:assembleDebug --stacktrace

[ArnyminerZ]

Heads up: this PR fixes adapter detection (KotlinAdapterLoader.kt, choosing the 2.4.0 adapter when the compiler exposes the new FIR extension registration API), but it doesn't touch KoinAnnotationProcessor.kt. It won't fix #89 (Kotlin 2.4.20) — that crash (IrUtilsKt.getValueArgument) happens inside the 2.4.0 adapter's own IR processing after it's already correctly selected, since 2.4.20 changed that IR util's signature. Worth tracking as a separate fix on top of this one.