v5.0.0 jdk25, enable semuru for kotlin, checkout via v6

What's Changed

• update files of remote gt to version v1.6.0 via gt by @tegonal-bot in #160
• set reviewer via api instead of create-pr action by @robstoll in #161
• add jdk25, axis also for Kotlin/Scala defaults by @robstoll in #162
• re-enable semuru also for Kotlin by @robstoll in #163
• format sh via shfmt by @robstoll in #164
• update checkout action to v6 by @robstoll in #165

Full Changelog: v4.2.0...v5.0.0