XWIKI-22458: Message boxes variant style does not match initial design

[Sereza7]

Jira URL

https://jira.xwiki.org/browse/XWIKI-22458

Changes

Description

• Updated style to get back the margin next to the icon on inline blocks.
• Updated style of standalone boxes to both:
  • fit the design agreed upon earlier
  • avoid style regression on old hard-coded boxes

Clarifications

• See comments in the code

Screenshots & Video

The style changes on inline messages are quick easy to test. However making sure that we did not break backward compatibility while making the new design was a bit more complicated. The first example shows various uses of the updated macro. The second and third example display some hard coded boxes that we can find in the UI: the second one contains a specific HTML content that did not work well with the style changes (one of the reasons to make the selector for new styles specific) -- the third one contains a hard coded icon.
Before the PR:



after the PR:

Executed Tests

Manual tests only, this is a style change.

Expected merging strategy

• Prefers squash: Yes
• Backport on branches:
  • None, same as changes for XWIKI-21452 brought in 16.7.0+