Forseti is an open-source project to build dependency graphs of your usage of GCP services. It's primarily designed for security but can be applied into other areas. You could extend the model to understand relationships between services and SLAs, but this would be limited to how you design and run services on top of GCP.

https://forsetisecurity.org/docs/latest/concepts/

To understand the underlying design of how each GCP service relates to each other is complex and definitely not available to the public. There is also a huge amount of nuance between GCP services relying on underlying Google services vs. other GCP services. Container Registry and Artifact Registry may both depend on the same underlying storage service, which isn't necessarily GCS, but could be an internal Google storage service. How this is specifically managed, partitioned and run is very hard to extract. Failure modes and scenarios are well designed and understood internally, but not shared publicly.

If you had a very specific use case you could approach your Google Cloud TAM/sales/customer engineer with the questions and they will be able to help you understand.

Source: Former Customer Engineer in Google Cloud for 4 years