[css-lists][css-counter-styles] Define which symbols are not affected by font-family, and how exactly #6201

If you have this code:

<!-- AdobeBlank defined in https://github.com/adobe-fonts/adobe-blank/blob/master/adobe-blank.css -->
<ol style="font-family: AdobeBlank">
  <li style="list-style-type: decimal">1.</li>
  <li style="list-style-type: circle">◦</li>
</ol>

Then the font displays both 1. of the ::marker and text node as blank.
But in the 2nd item, we still see the ◦ of the ::marker, only the text node is blank.

This was kinda explained in CSS2 https://www.w3.org/TR/CSS22/generate.html#list-style

Glyphs are specified with disc, circle, and square. Their exact rendering depends on the user agent

However, according to https://drafts.csswg.org/css-counter-styles-3/#simple-symbolic, circle is just supposed to produce a U+25E6 ◦, and CSS Lists doesn't say that ::marker should change the font-family or something.

So reading the specs I would guess that the ◦ should disappear too, but that's probably bad for compat.

So I think the specs should define what exactly happens. Implementations haven't been much consistent in the details:

• Is it just for list-style-type set to disc, circle, square, disclosure-open, disclosure-close? What if their definition is changed using @counter-style?
• What if I use my own @counter-style like

  @counter-style my-circle-1 { system: cyclic; symbols: "◦"; suffix: " "; }
  @counter-style my-circle-2 { system: extends circle; }

• What if I use list-style-type: "◦ " or ::marker { content: "◦ " }?
• What if I use ::after { content: counter(c, circle) }?