Rustdoc search: Increase relevance of primitive types

[killercup]

This minimally changes rustdoc's search as described in #25167.

Additionally, I also cleaned up some parts of the JS code.

There is one more change I made: After each result for a primitive type, I added "(Overview of primitive type)". This further differentiates the result from the module (previously, the only difference was that the module's link was blue). I'm not this is the way to go (this seems to be the only place where we do this) and it's no problem for me to remove that commit.

cc @steveklabnik (it concerns docs) and @alexcrichton (who made changes to rustdoc previously)

[rust-highfive]

r? @pcwalton

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[bluss]

This is a great idea. What do you think about just a simpler phrase like (primitive type) for the highlight?

[killercup]

@bluss, I like that. Italic, too?

[Gankra]

r=me with the (primitive type) hint updated as discussed.

[killercup]

@gankro thanks for the review. This is how it looks now:

[Gankra]

@bors r+ rollup

Awesome, thanks!

[bors]

📌 Commit 07b1994 has been approved by Gankro

[killercup]

@gankro I think bors picked the commit I just replaced. (Doesn't matter though, I only changed the commit message.)

[Gankra]

@bors r-

[Gankra]

@bors r+ ec60d

[Gankra]

(we'll see if that worked... the PR is certainly still approved in the queue...)

[killercup]

Thanks! :)

[steveklabnik]

@gankro@bors doesn't leave the message when you specify a commit hash, so i think this should be fine

[bluss]

Lol I didn't intend the italic. Either works.

[Gankra]

I liked the italic, and it's trivial to fiddle with later.