build: guard against duplicate classes using dependency analysis plugin

[sanjana2505006]

This PR introduces the Dependency Analysis Gradle Plugin (DAGP) to the build system to identify and guard against duplicate classes. This addresses the security risks associated with "Maven-Hijack" type attacks and helps ensure deterministic runtime behavior by preventing multiple dependencies from providing the same fully qualified class names.

Key Changes:

• Applied the com.autonomousapps.dependency-analysis plugin (v3.5.1) to the root project.
• Enabled the plugin specifically for the :grails-core module to provide a targetted security guard for the main codebase.
• Configured global issue severity to fail in the dependencyAnalysis block to ensure any detected duplicates break the build.

Verification: Ran ./gradlew :grails-core:projectHealth, which successfully caught an existing duplicate class conflict in the :grails-core module (between jcl-over-slf4j and spring-jcl). This confirms the guard is active and effective.

This PR fixes #15329

[jdaugherty]

I appreciate the PR for this but the examples show this as a settings plugin. We also have 4 separate gradle projects that use composite builds to combine into one (technically forge) so this change is incomplete. We also need to spend time testing this.

Can you please hold off on implementing newly opened tickets in the future? Or at least check before proceeding? This is one of those tickets that needed more investigation. While that plugin is probably the right immediate solution, we haven't discussed this in the weekly yet.

[sanjana2505006]

@jdaugherty Thank you for the context, I appreciate you explaining the broader setup and the concerns around the composite builds.
That makes sense, and I agree this needs more discussion and testing before moving forward. I didn’t fully factor in the impact across the other Gradle projects.
I’ll pause further work on this and wait for direction after it’s discussed in the weekly. Going forward, I’ll make sure to check in before proceeding on newly opened tickets that may need deeper investigation.

Thank you again for the guidance.

[jdaugherty]

I am going to convert this review back to a draft since this isn't complete.