Spike - Investigate CPU spend on Plan pages; such as epic, issue show page

The EpicsController#show action currently spends a lot of CPU time to render the view:

https://log.gprd.gitlab.net/goto/eedb4c20-b516-11ec-b73f-692cc1ae8214

We should investigate why this is and take action to reduce it, for example by:

• Moving code from view partials inline
• Moving common, reusable items into ViewComponents

Update 2022-05-03

This appears to be true of issues and other issue-based views also. See #358016 (comment 930693417)