chore: migrate from deprecated KotlinCompilerVersion and kotlinOptions to compilerOptions DSL

[marandaneto]

💡 Motivation and Context

The Kotlin Gradle Plugin deprecated KotlinCompilerVersion (scheduled for removal in Kotlin 2.2) and kotlinOptions/KotlinJvmOptions in favor of the new compilerOptions DSL.

This PR migrates all usages across the project to eliminate these deprecation warnings during CI builds, while maintaining the same compiler settings and compatibility targets.

💚 How did you test it?

• make compile — builds successfully with no deprecation warnings for KotlinCompilerVersion or kotlinOptions
• make testJava — all core tests pass
• make checkFormat — formatting is clean

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• No breaking change or entry added to the changelog.

If releasing new changes

• Ran pnpm changeset to generate a changeset file
• Added the "release" label to the PR to indicate we're publishing new versions for the affected packages

[github-actions]

posthog-android Compliance Report

Date: 2026-04-09 07:31:45 UTC
Duration: 197ms

✅ All Tests Passed!

0/0 tests passed

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[marandaneto]

still generates bytecode 52 so all good with the changes

[ioannisj]

LG, compiles for me as well