feat(Alert): Max-width with padding

What does this MR do?

Exploring using CSS calc to create a max-width of content within alerts. This would replace the effort in !910 (merged) that added additional markup and flexbox for the max width — an approach that works for GlAlert, but not for the HAML or Ruby alert instances without updating the markup for each instance.

Example behavior

• Integration MR: gitlab!50973 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Code review guidelines.
• GitLab UI's contributing guidlines.
• If it changes a Pajamas-compliant component's look & feel, the MR has been reviewed by a UX designer.
• If it changes GitLab UI's documentation guidelines, the MR has been reviewed by a Technical Writer.
• If the MR changes a component's API, integration MR(s) have been opened in the following projects to ensure that the @gitlab/ui package can be upgraded quickly after the changes are released:
  • GitLab: mr_url
  • CustomersDot: mr_url
  • Status Page: mr_url
• Added the ~"component:*" label(s) if applicable.

Security

N/A