Update to KorGE 6.0.0

[FSaurenbach]

@jobe-m if you merge this, please squash it because of the commit history

[Copilot]

Pull Request Overview

This PR updates the KorGE framework from version 6.0.0-beta4 to the stable 6.0.0 release and performs project cleanup by removing placeholder test files and adding standard Gradle configuration properties.

• Updates KorGE plugin version from beta to stable release
• Removes empty placeholder test files from the project
• Adds comprehensive Gradle configuration properties for better build performance and compatibility

Reviewed Changes

Copilot reviewed 4 out of 6 changed files in this pull request and generated no comments.

File	Description
gradle/libs.versions.toml	Updates KorGE plugin version from 6.0.0-beta4 to 6.0.0
gradle.properties	Adds standard Gradle configuration properties for memory, caching, and Kotlin settings
src/commonTest/kotlin/MyTest.kt	Removes placeholder test file
korge-virtualcontroller/src/commonTest/kotlin/org/korge/samples/mymodule/MyModuleTest.kt	Removes placeholder test file

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[FSaurenbach]

Should be working now. also kindly create a new tag 1.2.0 so it gets published to the store!

[jobe-m]

LGTM!

Thanks for the cleanup and update!