Auto merge of #108015 - matthiaskrgr:rollup-qerohjn, r=matthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - #107902 (fix: improve the suggestion on future not awaited)
 - #107913 (Update broken link in cargo style guide)
 - #107942 (Tighter spans for bad inherent `impl` self types)
 - #107948 (Allow shortcuts to directories to be used for ./x.py fmt)
 - #107971 (Clearly document intentional UB in mir-opt tests)
 - #107985 (Added another error to be processed in fallback)
 - #108002 (Update books)
 - #108013 (rustdoc: use a string with one-character codes for search index types)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors