Polish the block switcher styles

[jasmussen]

This PR adds a little polish to the block switcher.

• It normalizes padding, which fixes an alignment issue
• It adjusts hover colors
• It removes the arrow from the dropdown — I'm still chewing on this one but let's try out out for size

One thing that needs an extra pair of eyes is that I added a negative z index on .blocks-editable. It seems a recent change to that component added a position: relative; inline style. Which is fine, but it also caused the switcher to .. underlap, is that a word? ... the contents of the block, regardless of how high a z index the switcher had. By giving the editable a negative z index this fixes that. But I can't quite predict the consequences.

[youknowriad]

Should the hover style of the block switcher be similar to the other controls?

[jasmussen]

Should the hover style of the block switcher be similar to the other controls?

Maybe :D — I should have clarified that this is another thing I'm trying on for size and may revert on.

This PR at least reduces the hover styles to two:

1. action buttons, which have a blue hover style
2. toggles, which have a bordered outline hover style with no text color change

My reasoning for style #2 is that this is what WordPress does at the moment for toggle buttons like bold, italic etc. We might find that this isn't solid, and in that case I'd like to try a unified singular hover style for all things. Which is likely to be different from both the two above, btw.

But for now, I'm hoping we can try this and get a feel for it.

[youknowriad]

In #460, I felt that the style #2 is not ideal. Too many black background (especially when we have multiple inline formats applied), I tend to prefer the design we had in the prototypes.

By giving the editable a negative z index this fixes that. But I can't quite predict the consequences.

I don't know the consequences either. It could have an impact on the "floating blocks" maybe, but fine to address when we see a problem.

Anyway this is good to merge as is. 🚢

[jasmussen]

Thank you Riad!

I agree the dark style can be a bit heavy. But it's one of the styles that passes the accessibility guidelines. Let's keep our ideas flowing but move forward, a little bit at a time :)

[ellatrix]

@jasmussen Hm, adding the z-index made the editable fields unfocusable. Any reason this was added?