Gradle build refactoring and version upgrade (6 to 8) :rocket::rocket:

[dejan2609]

details:

• gradle: 6.8.2 -->> 8.6
• gradle 'launch4j' plugin: 2.4.9 -->> 3.0.5
• gradle 'shadow' plugin is introduced (but gradle build is simplified)
• gradle configurations are changed: 'compile' is replaced with 'implementation' 'testCompile' is replaced with 'testImplementation'

related links:

• https://docs.gradle.org/8.6/userguide/upgrading_version_6.html#sec:configuration_removal
• https://docs.gradle.org/8.6/userguide/upgrading_version_8.html#java_convention_deprecation
• https://docs.gradle.org/8.6/dsl/org.gradle.api.plugins.JavaPluginExtension.html#org.gradle.api.plugins.JavaPluginExtension:sourceCompatibility
• https://docs.gradle.org/8.6/javadoc/org/gradle/api/JavaVersion.html