Rollup merge of rust-lang#85699 - ehuss:update-books, r=ehuss

Update books

## reference

4 commits in 5aa457bf1b54bd2cd5d4cf49797f29299bdf89a7..9c68af3ce6ccca2395e1868addef26a0542e9ddd
2021-05-05 08:39:22 -0700 to 2021-05-24 09:53:32 -0700
- missing parameter name in Trait Implementations (rust-lang/reference#1030)
- Add more content to impl-trait.md (rust-lang/reference#1017)
- Document extended key-value attributes (rust-lang/reference#1029)
- Document raw pointer <-> usize casts. (rust-lang/reference#970)

## rust-by-example

1 commits in 5f8c6da200ada77760a2fe1096938ef58151c9a6..805e016c5792ad2adabb66e348233067d5ea9f10
2021-04-29 08:08:01 -0300 to 2021-05-20 17:08:34 -0300
- Update structs.md (rust-lang/rust-by-example#1440)

## rustc-dev-guide

4 commits in 1e6c7fb..50de7f0
2021-05-10 13:38:24 +0900 to 2021-05-20 15:02:20 +0200
- update rustfmt references to reflect change from submod to subtree (rust-lang/rustc-dev-guide#1129)
- Remove `--stage 1` argument from `doc` invocations (rust-lang/rustc-dev-guide#1125)
- Update coverage docs (rust-lang/rustc-dev-guide#1122)
- Document -Zunpretty=thir-tree (rust-lang/rustc-dev-guide#1128)

## edition-guide

1 commits in 1da3c411f17adb1ba5de1683bb6acee83362b54a..302a115e8f71876dfc884aebb0ca5ccb02b8a962
2021-02-16 16:46:40 -0800 to 2021-05-21 10:46:11 -0400
- Minimize the edition guide (rust-lang/edition-guide#232)

## embedded-book

1 commits in 569c3391f5c0cc43433bc77831d17f8ff4d76602..7349d173fa28a0bb834cf0264a05286620ef0923
2021-04-07 08:32:11 +0000 to 2021-05-25 13:59:05 +0000
- Remove $ from cargo-binutils  (rust-embedded/book#292)