[CHORE/#35] Improve test environment and add unit tests

[angryPodo]

Summary

This PR improves the project's testing infrastructure by upgrading to Java 17 and Kotlin 2.3.0, and adding comprehensive unit tests for core logic.

Related Issue

Closes #35

Details

• Environment Upgrade:

  • Upgraded project to Java 17 and Kotlin 2.3.0.
  • Adopted JUnit 6 as the main test framework.

• Unit Test Implementation:

  • Added unit tests for wisp-processor (Mapper, Validator) and wisp-runtime (Parser, Matcher).
  • Replaced MockK with Mockito for stable KSP object mocking.
  • Used Robolectric for testing Android-dependent code.

• CI Enhancement:

  • Configured a GitHub Actions workflow (ci.yml) to automatically run ktlintCheck, test, and assembleDebug on PRs and merges.
  • Applied the latest Gradle caching strategies for performance.

• Known Issue:

  • KSP integration tests using KotlinCompileTesting were excluded due to a persistent IllegalStateException in the Kotlin 2.3.0 environment. Core logic is covered by unit tests.