Draft: Introduce pipelines app refactor to GraphQL/Subscriptions

What does this MR do and why?

Introduce pipelines app refactor 🚀

👇 All progress towards this effort can be seen in the table below 👇

MR Link	Description	Stack
!210777 (merged)	Add pipeline subscriptions for projects	Backend
!206072 (merged)	FF creation and core architecture setup	Frontend
!207467 (merged)	Pipeline mini-graph and button actions	Frontend
!208865 (merged)	Pagination	Frontend
!209348 (merged)	Empty state, tabs/nav	Frontend
!210021 (merged)	All count, scope and query params	Frontend
!209716 (merged)	Emit table actions for pipeline actions	Frontend
!210372 (merged)	Filtered search ability and ID/IID toggling	Frontend
!207476 (merged)	Add new pipeline type fields	Backend
!211323 (merged)	Implement subscription	Frontend
!211655 (merged)	Fix any missing pieces	Frontend
!212131 (merged)	Merge new pipelines from subscription	Frontend
!212441 (merged)	Delimiter and count loading improvement	Frontend
!212468 (merged)	Fix empty state logic for pipeline controls	Frontend
!213708 (merged)	Fix filter by source and yaml errors	Frontend
!212637 (closed)	Feature flag cleanup and code removal	Frontend/Backend

References

Screenshots or screen recordings

How to set up and validate locally

1. Visit Project > Build > Pipelines
2. Ensure feature works as should
3. Ensure all code that can be cleaned up is cleaned up

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #223264