Investigate `derailed` report not flagging addition of `action_cable/engine`

Broken out of https://gitlab.com/gitlab-org/memory-team/team-tasks/-/issues/39

We currently run derailed-benchmarks as part of CI and expose results via Danger (in the Metrics report.) The idea here is that if we detect an increase in memory consumption compared to the previous result, a warning is issued (similarly to how a reduction on code quality is flagged.)

We recently introduced ActionCable to application.rb, but the metrics report did not pick up that this added a substantial amount of new memory being consumed.

Goals/deliverables:

• Investigate why including action_cable/engine was not reported to increase memory consumption (the boot memory metrics should pick this up, as it happens in application.rb)
• Produce a fix or follow-up issue outlining a solution