Pattern & Media List Items: Use consistent admin focus style

[richtabor]

Let's update the focus state style applied to Inserter list items, so that it is in line with what we employ throughout the experience.

Current

Expected

[richtabor]

Could very well be related:

[mikachan]

I believe this should be fixed with #50819. Please re-open if not!

[juanfra]

From what I see in #50819 we're adding changes to the hover state of the icon. I believe those changes are not fixing what was initially reported in this issue, which concerns the focus style.

By inspecting the elements, I see that the styles for the image under "current" is using the border property for the focus style whereas we use an inset box-shadow in other places. It'll likely be fixed by adjusting the focus style for the "item group" component.

[mikachan]

Good spot, @juanfra. I've opened another PR to address this: #51576

[juanfra]

Thanks for working on this, Sarah 😄