Provide better snapshoting UX to source options buckets

[lacasseio]

The source options bucket paths are captured as a value. We should either try to force them as files but it must not break the incrementalness. Alternatively, we could register the paths as a map where the key is the path and a dummy value. It would force Gradle to list the path in the build scan.

Either way, it would provide insight into what file participates in which bucket. The still open question is how to provide insight in which action was used to configure the bucket. We could do a similar trick and use the action's toString if implemented else use a computed value.