build: Add Kotlin to the project

[agrognetti]

• Added the 'org.jetbrains.kotlin.android' plugin to all module build.gradle files and configured the Kotlin compiler JVM target to 1.8 in the root build.gradle.
• Updated the buildscript to use Kotlin version 2.2.0 and included the Kotlin Gradle plugin classpath.

Requirements

• I have added test coverage for new or changed functionality
• I have followed the repository's pull request submission guidelines
• I have validated my changes against all supported platform versions

Describe the solution you've provided
I've added the Kotlin plugin and the configuration needed to be able to add Kotlin code in future PRs

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Note

Adds Kotlin support to all modules and configures the Kotlin Gradle plugin with JVM target 1.8 in the root build.

• Build/Gradle:
  • Add Kotlin Gradle plugin (kotlin_version = 2.2.0) and classpath in root build.gradle.
  • Configure KotlinCompile tasks with jvmTarget = 1.8 for all subprojects.
  • Apply org.jetbrains.kotlin.android plugin to contract-tests, example, launchdarkly-android-client-sdk, and shared-test-code modules.

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