Field-required indicators need to be pure CSS rather than markup

Problem/Motivation

The "form-element" and "fieldset" components add markup after the label/legend when a form element is required. (A text-danger span containing an asterisk.)

The required status of an element can be altered by javascript triggered by the "#states" API. This won't add/remove the markup, so the element's appearance won't be updated to indicate its new status.

Steps to reproduce

Alter a form to add the required #states to an element depending on the status of another.

The required indicator is not added/removed.

Proposed resolution

Core themes add this marker purely as CSS. Radix should remove the markup from these components and add the required styles.

Olivero has the following style that does this:

/* Form required star icon */

.form-item__label.form-required::after,
.fieldset__label.form-required::after,
.required-mark::after {
  display: inline-block;
  width: 0.5rem;
  height: 0.5rem;
  margin-inline: 0.3em;
  content: "";
  vertical-align: text-top;
  /* Use a background image to prevent screen readers from announcing the text. */
  background-image: url("data:image/svg+xml,%3Csvg height='16' width='16' xmlns='http://www.w3.org/2000/svg'%3E%3Cpath d='m0 7.562 1.114-3.438c2.565.906 4.43 1.688 5.59 2.35-.306-2.921-.467-4.93-.484-6.027h3.511c-.05 1.597-.234 3.6-.558 6.003 1.664-.838 3.566-1.613 5.714-2.325l1.113 3.437c-2.05.678-4.06 1.131-6.028 1.356.984.856 2.372 2.381 4.166 4.575l-2.906 2.059c-.935-1.274-2.041-3.009-3.316-5.206-1.194 2.275-2.244 4.013-3.147 5.206l-2.856-2.059c1.872-2.307 3.211-3.832 4.017-4.575-2.081-.402-4.058-.856-5.93-1.356' fill='%232494DB'/%3E%3C/svg%3E%0A");
  background-repeat: no-repeat;
  background-size: 0.5rem 0.5rem;
}

And Claro does this:

.form-item__label.form-required::after,
.fieldset__label.form-required::after {
  display: inline-block;
  margin-inline: 0.15em;
  content: "*";
  color: var(--color-maximumred);
  font-size: 0.875rem;
}

I replaced the "__" in the rules with spaces, and Olivero's solution worked for me. (Although I don't love the color. ;) But that's easily changed.)