Content Authoring Experience refinement following CET UAT

Summary

Sprint 8, release 4. Intended to address feedback and issues from CET's UAT sessions.

Tickets included

• https://digitaldevelopment.atlassian.net/browse/D8NID-721
• https://digitaldevelopment.atlassian.net/browse/D8NID-755
• https://digitaldevelopment.atlassian.net/browse/D8NID-781
• https://digitaldevelopment.atlassian.net/browse/D8NID-777
• https://digitaldevelopment.atlassian.net/browse/D8NID-742
• https://digitaldevelopment.atlassian.net/browse/D8NID-666
• https://digitaldevelopment.atlassian.net/browse/D8NID-650
• https://digitaldevelopment.atlassian.net/browse/D8NID-297

Core, contrib or third-party package updates

N/A