Change `cargo fix --edition` to only fix edition lints.

This changes it so that `cargo fix --edition` will only fix edition lints.  The reason for this is that sometimes non-edition lints get in the way, and make suggestions that can cause failures.  An example is a user that only ever runs `cargo test` or `cargo check --profile=test` locally, and doesn't realize there are problems with running without `cfg(test)` such as unused warnings.

This works by using `--cap-lints=allow` along with `--force-warn` which takes precedence over `cap-lints`.

This only works on nightly since `--force-warn` is still unstable.  I will update this as part of #9800.

Closes #5738

Update cargo, books

## nomicon

2 commits in 0c7e5bd1428e7838252bb57b7f0fbfda4ec82f02..fe6227eb3c8533200c52dffa42ef1b6f2f02c40e
2021-08-04 10:18:22 -0700 to 2021-08-31 05:42:38 +0900
- update lifetime-elision to show what elided code under `rust_2018_idi… (rust-lang/nomicon#306)
- Change code for `into_iter` on the `RawVec` section for consistency/soundness (rust-lang/nomicon#302)

## cargo

8 commits in f559c109cc79fe413a8535fb620a5a58b3823d94..18751dd3f238d94d384a7fe967abfac06cbfe0b9
2021-08-26 22:54:55 +0000 to 2021-09-01 14:26:00 +0000
- print the full destination path when no track duplicates (rust-lang/cargo#9850)
- Stabilize 2021 edition (rust-lang/cargo#9800)
- Stabilize patch-in-config (and prefer config over manifest) (rust-lang/cargo#9839)
- Adding the cargo doc --examples subcommand (rust-lang/cargo#9808)
- Make library created with `cargo new` clippy happy (rust-lang/cargo#9796)
- Swap out some outdated repo urls in documentation (rust-lang/cargo#9862)
- Change `cargo fix --edition` to only fix edition lints. (rust-lang/cargo#9846)
- Show desc of well known subcommands (fmt, clippy) in cargo --list (rust-lang/cargo#9848)

## reference

1 commits in da6ea9b03f74cae0a292f40315723d7a3a973637..0e5ed7a4bec065f0cc18c35d1c904639e095314d
2021-08-19 21:28:10 -0700 to 2021-08-29 17:33:21 +0900
- expressions.md: Attempt fixing broken grammar in Mutability paragraph (rust-lang/reference#1084)

## book

1 commits in 687e21bde2ea10c261f79fa14797c5137425098d..fcb5e0ea68112d85a1d29a7a7335978ef2a02181
2021-08-18 20:48:38 -0400 to 2021-08-31 21:26:19 -0400
- Improve the reading of the code (rust-lang/book#2845)

## rustc-dev-guide

7 commits in cf0e151..95f1acf
2021-08-22 11:47:02 -0300 to 2021-08-31 12:38:30 -0500
- Add link to `Span`
- Add rustc-source to suggested rust-analyzer config (rust-lang/rustc-dev-guide#1189)
- Fix typo, clarify backtick wording, and use inline code
- Trailing date comments in a line inside of a paragraph caused beginning of a new paragraph. (rust-lang/rustc-dev-guide#1196)
- Fix warning "Renderer command uses a path relative to the renderer output directory ..." (rust-lang/rustc-dev-guide#1194)
- Fix a code block containing ```rust
- date-check: Recognize capitalized 'Date' as well

## edition-guide

1 commits in 3710b0cae783d0bcd2b42452a63b081473f5970a..2d9b1b9da706de24650fdc5c3b0182f55c82115d
2021-07-26 11:34:46 -0700 to 2021-08-31 10:44:09 +0200
- Update for 2021 stabilization (rust-lang/edition-guide#266)

## embedded-book

1 commits in 4f9fcaa30d11ba52b641e6fd5206536d65838af9..c3a51e23859554369e6bbb5128dcef0e4f159fb5
2021-08-06 17:43:12 +0000 to 2021-08-26 07:04:58 +0000
- Make glossary more linkable and add more detail  (rust-embedded/book#299)

Fix `cargo fix --edition` on stable.

I accidentally missed the removal of a `-Zunstable-options` flag in #9800.  This prevented `cargo fix --edition` from working on stable/beta.