Pass proper theme colors for inlays and suggestions (#3517)

<img width="1728" alt="image"
src="https://github.com/zed-industries/zed/assets/2690773/f6f1e24f-71fe-4a2e-9bcf-9e98861c0da4">


![image](https://github.com/zed-industries/zed/assets/2690773/8434d8a1-ee7e-49c1-9e88-362363225d96)

Now inlays are visible in all zed2 themes, but 
* always have a blue color which is the same as some theme colors
* not other hint-related style changes like font width, background, etc.
seem to exist in the theme, ergo not propagated.

In general though, people want those style changes applied to their
hints, so we might want to do something about it later.
I've left a `// todo!("what about the rest of the highlight style parts
for inlays and suggestions?")` in the corresponding places for that.

Release Notes:

- N/A