Structs/enums variant don't have a way to make an anchor in rust doc

[GuillaumeGomez]

Currently, we have to look into the HTML directly if we want to give an anchor to a struct/enum variant. We should use the same way we do for other methods/functions/types.

Also, the generated symbol should be before, it'd allow to remove any potential issue of space we encountered recently.

cc @rust-lang/docs

[GuillaumeGomez]

And working on it of course

[GuillaumeGomez]

Oh it has been merged through #44661.