Add descriptions to all icons in the Admin Tools Notifications page

[ameliav]

🗣 Description

Add descriptions to all icons in the Admin Tools Notifications page
JIRA CRASM-354 for 508 compliance

💭 Motivation and context

The Icons on the Admin Tools Notifications page are missing alternative text. Provide concise and meaningful text alternates for all non-text content. The description needs to provide enough information so that the purpose of non-text content can be understood even if it is removed.

🧪 Testing

In the console, all the icons have aria-labels that describe what the icon looks like and its purpose

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• All future TODOs are captured in issues, which are referenced
  in code comments.
• All relevant type-of-change labels have been added.
• I have read the CONTRIBUTING document.
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated
  to reflect the changes in this PR.
• Tests have been added and/or modified to cover the changes in this PR.
• All new and existing tests pass.

✅ Pre-merge checklist

• Revert dependencies to default branches.
• Finalize version.

✅ Post-merge checklist

• Create a release.

[aloftus23]

Built local and tested. Loots good!

[schmelz21]

LGTM