feat: Android - downgrade Kotlin to 2.0.21, upgrade JVM to 11

[abelonogov-ld]

Summary

• Increase compatibility and gives more Java features

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Note

Medium Risk
Build-toolchain and dependency version shifts (Kotlin/JVM targets plus coroutines/serialization downgrades) can cause compilation or runtime compatibility issues across consumers despite minimal code changes.

Overview
Shifts the Android toolchain to Kotlin 2.0.21 (plugin versions updated) while moving the observability-android library and the MAUI LDObserve native Android module to Java/JVM 11 (sourceCompatibility/jvmTarget).

To keep Kotlin 2.0.21 compatible with transitive dependencies, the library build now pins Kotlin runtime artifacts (kotlin-stdlib/reflect/test) to 2.0.21 and downgrades coroutines/serialization versions accordingly; it also bumps launchdarkly-android-client-sdk to 5.12.0.

Fixes a Kotlinx serialization call-site by switching GraphQLClient request encoding to the explicit encodeToString(serializer, value) form, and updates the e2e app’s noCompose flavor to include androidx.activity:activity-ktx:1.7.0 for by viewModels() support.

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Cursor Bugbot has reviewed your changes and found 1 potential issue.

There are 2 total unresolved issues (including 1 from previous review).

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