<figure> elements with a role of group need an accessible label

Problem/Motivation

In Add role="group" to to meet WCAG requirements, comment #22 is correct that if a <figure> has a role of group, it needs an accessible name from an aria-label or aria-labelledby attribute. This role is now provided by default in the media component, but has no accessible label.

Steps to reproduce

1. Start with a clean install of Drupal 9, using Bartik or other default themes.
2. Create a new basic page and select "Add media" from the toolbar
3. Upload an image, and select the "caption" checkbox
4. Fill out the caption value beneath the image and save the page.

What should happen: the final markup should render one of two patterns.

<figure role="group" aria-label="Accessible label"/>
  <img.../>
  <figcaption>Figcaption text</figcaption>
</figure>

<figure role="group" aria-labelledby="id-of-accessible-name-text"/>
  <img.../>
  <figcaption id="id-of-accessible-name-text">Figcaption text</figcaption>
</figure>

What currently happens: the figure has a role of group, but no accessible name tied to it.

<figure role="group">
  <img.../>
  <figcaption>Figcaption text</figcaption>
</figure>

Proposed resolution

One of (maybe) three solutions should be acceptable:

1. adding core support for an aria-label value an editor can provide, which populates the aria-label attrbute
2. Adding an auto-generated ID value to the <figcaption> or some other text name for the <figure>, and add an aria-labelledby attribute to <figure> with a value of that ID.
3. I saw the thread on possibly removing the role from core: Remove role="group" from figure in FilterCaption output. It's another way to go to resolve this particular issue, but also sounds like that's postponed. If a move in that direction isn't immediate, then there should be a patch for adding an accessible name by default until that change happens.

Remaining tasks

Remaining work needs to be defined depending on the preferred approach.