Ensure correct content in pipeline graph when more than 2 upstream or downstream are present

Summary

After fixing the issue that prevented the expansion of upstream and downstream nodes in the pipeline graph (#119017 (closed)) it came to my attention that the API limits the number of depth to 3. This is due to performance reason (See !27029 (comment 312010955)), but currently because the API returns nothing on the last pipeline, the graph doesn't even show that there is another node which is confusing.

How to reproduce

Create a graph with 4 pipelines related (1,2,3,4) each being downstream of the previous one. When you open up 3, it will not show that any relationship exists between 3 and 4. If you look in the network tab, you can also see that 3 will not have the property triggers.

Proposed solution

Now that the performance concerns have been addressed, we should show all the links to upstream and downstream pipelines and allow the user to open them, just like we currently do for the first 3 related pipelines, but that behavior should extend to any number of downstream pipelines.

The UX can remain the same, we would just fix the problem with the pipelines not showing up once you're 3 related pipelines deep.

Note: This will become a lot easier to impliment (if it doesn't happen automatically) once the work in #276949 (closed) has been completed