Update Gradle wrapper, plugins, and multiple dependencies

[0xSoul24]

This pull request includes several upgrades to dependencies, build plugins, and the Gradle wrapper, along with an important bugfix for resource pack conversion. The main themes are: updating to newer library and plugin versions for better compatibility and features, and improving the robustness of the resource pack conversion process to handle unsupported model transforms.

Dependency and Plugin Upgrades:

• Upgraded com.google.code.gson to 2.13.2, commons-io to 2.21.0, com.twelvemonkeys.imageio-tga to 3.13.1, and various net.kyori:adventure libraries to 4.26.1 in converter, pack-schema/api, and pack-schema/bedrock modules for improved stability and feature support. [1] [2] [3] [4]
• Updated io.freefair.lombok from 8.6 to 9.2.0 in converter/build.gradle.kts.
• Updated com.formdev:flatlaf and flatlaf-intellij-themes to 3.7.1 in bootstrap/build.gradle.kts.

Build System and Plugin Changes:

• Switched from com.github.johnrengelman.shadow to com.gradleup.shadow Gradle plugin throughout the project, including in bootstrap/build.gradle.kts, build-logic/build.gradle.kts, and build-logic/src/main/kotlin/pack.publish-conventions.gradle.kts, and updated related configuration. [1] [2] [3]
• Updated the Gradle wrapper from 8.6 to 9.4.1, with related script and property changes for improved build reliability and compatibility. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]

Bugfixes and Conversion Improvements:

• Improved the resource pack conversion process in PackConverter.java to handle unsupported model transforms (e.g., "on_shelf") by copying and patching JSON files before loading, preventing enum deserialization errors and providing clearer error messages for malformed packs. [1] [2] [3]

CI/CD Workflow Update:

• Updated GitHub Actions workflow to use actions/upload-artifact@v7 instead of v4 for artifact archiving. (.github/workflows/pullrequest.yml)

[SleepyPopp]

The on_shelf fix seems unnecessary because it's fixed when PackConverter uses Nexo's creative fork (#55).

[SleepyPopp]

Please do not use AI to generate PR descriptions. You should be able to explain what you did in your PR.

[SleepyPopp]

In the future, when submitting PRs, please be transparent with any AI tool used to assist with your code, along with what extent the tool was used for.