UI - View related data entity list on Category page without delay

[nateiam]

As a Business Analyst I want to rapidly view the list of related data entities on the Category page so I can scan quickly through the list to choose where to drill down.

Tech Note - this involves replacing existing calls for BDef keys and details with a single call to the BDef Search endpoint described in #222

Acceptance Criteria

• Related data entities list appears almost immediately upon navigating to that section of the page
• Related data entities list is otherwise unchanged from existing