Rollup merge of #84380 - Smittyvb:rdoc-title-order, r=jsha

Write Rustdoc titles like "x in crate::mod - Rust"

This makes Rustdoc titles for items be like "Widget in cratename::blah::foo - Rust". Titles for modules and other non-items are unchanged, and still read like "cratename::blah::foo - Rust". This makes managing several open Rustdoc tabs easier.

![A screenshot of several open Rustdoc tabs](https://user-images.githubusercontent.com/10530973/115457675-d608f180-a1f2-11eb-87a8-838a32b4e3f7.png)

This also adds some tests for the new title behavior.

Closes #84371.