Style nested <ul>s with circles instead of normal bullets

[chrisvanpatten]

Discovered while working on #10303 that we style nested unordered lists with a normal bullet, instead of circle which is more typical of user agent stylesheets (aka default browser styles).

In the Chrome user agent styles, for instance, you can see the default is overridden:

This adds a rule to the editor stylesheets to handle nested styles.

Here's the before:

And here's the after:

One small implementation note: I've removed a :not() selector that was previously ensuring the <ul> CSS rule did not apply to .wp-block-gallery and instead placed an override in the gallery block's editor stylesheet.

I expect this to be slightly controversial, but this is intentional to avoid a selector specificity issue. Basically, ul:not(.wp-block-gallery) is more specific than ol ul. We would have had to do something like ol:not(.wp-block-gallery) ul or whatever to increase the specificity which is kind of annoying and unnecessary. To me, this feels like a case where the gallery should manage its own overrides.

[chrisvanpatten]

(As it so often is, the Travis failure seems unrelated.)

[tofumatt]

This makes a lot more sense to me code-wise. The editor styles specifically :not() targeting a single block's styles rather than that block managing it seems hacky/inelegant. I like this solution way more.

I haven't tested this locally but I prefer this approach. 👍 on the code aspect.

[chrisvanpatten]

Thanks @tofumatt! I'll still wait for an "OK" from a design person before merging since this is technically a visual change :)

[chrisvanpatten]

@jasmussen Sorry to ping just want to see if I can get a visual OK on this so I can get it in today :)

[jasmussen]

Apologies for missing this.

I think this is good to go. No strong opinion, but also no objections. 👍 👍

[chrisvanpatten]

Thanks @jasmussen and no worries for missing it! ^__^