fix(image-redundant-alt): prevent redundant issues of image tree

[straker]

The image-redundant-alt rule applied to more than just buttons and links (as the help text stated). It also was being applied to p, li, td, and th elements. This caused a single image to be reported multiple times if it's parent tree consisted of each of those elements:

<td>
  <p>
    <button>
      <img alt="Alt text">
      Alt text
    </button>
  </p>
</td>

This changes the rule to focus only on img elements and look up the tree for the button, [role=button], a[href], p, li, td, and th elements and check the text against the image alt. This way only the image node will throw the error and not each parent node.

Linked issue: #1416

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• Follows the commit message policy, appropriate for next version
• Has documentation updated, a DU ticket, or requires no documentation change
• Includes new tests, or was unnecessary
• Code is reviewed for security by: @WilcoFiers

[WilcoFiers]

Very minor point.

Resolved