Gutenberg: 9.8 upgrade

[sirreal]

Previous upgrade: #48771
Release notes:

• v9.8.0
• v9.8.1
• v9.8.2
• v9.8.3

Process

• Install and activate
  • Copy install activate on edge (D55451-code)
  • Edge was reverted and should be redeployed (issue fixed by D55432-code)
  • Copy 9.7.4 to 9.8.1 (D55827-code)
  • Install activate 9.8.1 on edge (D55922-code)
  • Install activate 9.8.2 on edge
  • Copy 9.8.2 to 9.8.3 (D56301-code)
  • Install 9.8.3 (D56307-code)
  • Activate 9.8.3 on edge (D56309-code)
  • Activate on production sites (D56316-code)
  • Request update for Atomic sites (p9o2xV-1f5-p2)
• Testing
  • Calypso E2E (Gutenberg: Trigger E2E edge tests for v9.8.x #48960, empty commit to trigger e2e tests for gb 9.8.3 on edge #49558)
  • TC (D55935-code)
• Publish internal announcements (p7DVsv-aoC-p2)
• Update the Gutenberg Upgrade Log [pcoGjb-u-p2] and list patches applied.
• Open a new issue for the next upgrade, transfer remaining tasks, close this issue. (Gutenberg: 9.9 upgrade #49534)
• Roll back Editor: Hide plugin buttons in header on mobile layouts #49329 (can ping someone via pbAok1-1PR-p2#comment-3849)

Issues / Blockers 🐛

Cover block invalidates some attributes D55431-code
WordPress/gutenberg#28242
WordPress/gutenberg#28221 (also present in 9.7)
WordPress/gutenberg#28627

Fixes

…

FYI: @Automattic/good-mountain @tyxla @flootr @saramarcondes @griffbrad @inaikem

[fullofcaffeine]

This is done. Next one: #49534.