rustdoc: Show tag / badge / icon / emoji in the sidebar for unsafe, deprecated and unstable items

[tyilo]

Currently unsafe, deprecated and unstable items are shown with different labels in a module's list of items:

I think it would be nice to also add these to the sidebar for types and traits.
Maybe this requires icons for "Deprecated" and "Experimental" as well to not make the sidebar to wide.

[BD103]

By sidebar, do you mean the bar on the left of this screenshot?

I created the following with dev tools. I especially like the test tubes for experimental APIs, unsure about the other emojis.

[tyilo]

By sidebar, do you mean the bar on the left of this screenshot?

Yes, exactly what I meant.

Nice symbols too :)

[lolbinarycat]

Personally it seems odd to prefix the symbols in the sidebar, when in the module view they are suffixed.

[Scripter17]

I don't suppose there's any demand for a "this got stabilized recently!!!" icon?

If so then I nominate 🎉 because apparently there isn't a diploma emoji to go with the beaker/test tube theme for experimental stuff

I assume there won't be one but I want to make sure it's considered

[lolbinarycat]

I don't suppose there's any demand for a "this got stabilized recently!!!" icon?

IMO rustdoc already has enough machinery that is only used for std/core/alloc and nothing else.

[daniel-pfeiffer]

This is so welcome! How many times have I hopefully clicked on a promising sounding name, only to find it’s not for normal use…

[lolbinarycat]

possible duplicate of #67869, although this issue is more descriptive in exactly what changes are desired.