Bump shadow plugin, retaining OTel logging plugins

[cmgrote]

Note

Upgrades the Shadow plugin and replaces the custom transformer with a task that manually merges Log4j2 plugin caches during shadowJar.

• Build/Gradle:
  • Shadow plugin: Bump com.gradleup.shadow to 9.2.2 in gradle/libs.versions.toml.
  • Log4j plugins merging:
    • Replace Log4j2PluginsCustomTransformer with mergeLog4jPlugins task that collects and merges Log4j2Plugins.dat from runtime classpath using PluginCache.
    • Update tasks.shadowJar to depend on mergeLog4jPlugins, exclude existing Log4j2Plugins.dat, and include merged output under META-INF/.../plugins.
    • Remove related transformer imports and the custom transformer class from package-toolkit/runtime/build.gradle.kts.
  • Keep mergeServiceFiles() and existing dependency inclusions; no functional changes to published artifacts config.

^{Written by Cursor Bugbot for commit e9703a9. This will update automatically on new commits. Configure here.}