Fix circular dependency for minify/dexguard

[markushi]

📜 Description

Based on the task graph for R8/DG, mergeDex<Variant> is the closest to minify<Variant>WithR8.

1. hooked ProGuard UUID gen task to the minify/mergeDex tasks
2. hooked UUID upload to assemble task (same as source context)

💡 Motivation and Context

Fixes #679

Not sure if we still need transformClassesAndResourcesWithProguardTransformFor*!?

💚 How did you test it?

Manual testing with example app.

📝 Checklist

• I reviewed the submitted code
• I added tests to verify the changes
• I updated the docs if needed
• No breaking changes

🔮 Next steps

[romtsn]

LGTM!