Make `Expand all` button more visible

This is a follow-up from #232820 (comment 402228466):

image

  1. Improve text of “Too many changes to show” alert (#243572 - closed)
  2. This issue: Move the Expand all button to the left, after the comparison dropdowns, so it is more visible.
  3. Clarify “Expand all” button label (#243574 - closed)
Edited by Pedro Moreira da Silva