Upgrade gradle to 9.2.1

[syusui-s]

Upgrade Gradle from version 8 to version 9.

Changes

• Update Gradle version from 8.4 → 9.2.1
• Fix deprecated features in Gradle 9
  • Use multiline-string notation for dependencies

    • Declaring dependencies using multi-string notation has been deprecated. This will fail with an error in Gradle 10. Please use single-string notation instead: ... . Consult the upgrading guide for further information: https://docs.gradle.org/9.1.0-rc-4/userguide/upgrading_version_9.html#dependency_multi_string_notation

• Update plugins
  • shadow

Motivation

• Improve long-term maintainability