Rollup merge of rust-lang#91620 - ehuss:update-books, r=ehuss

Update books

## nomicon

1 commits in c6b4bf831e9a40aec34f53067d20634839a6778b..49681ea4a9fa81173dbe9ffed74b4d4a35eae9e3
2021-11-09 02:30:56 +0900 to 2021-11-24 16:27:28 +0900
- Clarify that drop flag fields only apply to older Rust versions (rust-lang/nomicon#324)

## reference

2 commits in c0f222da23568477155991d391c9ce918e381351..954f3d441ad880737a13e241108f791a4d2a38cd
2021-11-22 10:30:57 -0800 to 2021-11-29 11:11:30 -0800
- Say that bare trait objects are rejected in the 2021 edition (rust-lang/reference#1111)
- Update 'Subtyping and Variance' example to use `dyn Trait` syntax (rust-lang/reference#1110)

## book

5 commits in a5e0c5b2c5f9054be3b961aea2c7edfeea591de8..5f9358faeb1f46e19b8a23a21e79fd7fe150491e
2021-11-19 17:06:19 -0500 to 2021-12-05 21:33:16 -0500
- 1.57
- Update to 1.56
- Snapshot of ch 11 for nostarch
- Clarify how to check for an error in tests returning Result
- Update book repo links for default branch rename

## rust-by-example

1 commits in 43f82530210b83cf888282b207ed13d5893da9b2..1ca6a7bd1d73edc4a3e6c7d6a40f5d4b66c1e517
2021-11-21 22:31:50 -0300 to 2021-11-23 17:48:53 -0300
- Removed `u32` at the end of ints (rust-lang/rust-by-example#1477)

## rustc-dev-guide

10 commits in a2fc963..a374e7d
2021-11-18 13:31:13 -0500 to 2021-12-03 09:26:47 -0800
- Update LLVM coverage mapping format version supported by rustc (rust-lang/rustc-dev-guide#1267)
- Improve 'Running tests manually' section
- Fix some links
- Update for review comments.
- Document rustfix-only-machine-applicable
- Apply suggestions from pierwill
- Document more compiletest headers.
- make it compile with 1.56.0 no warning
- make it compile with 1.56.0
- make it compile with 1.56.0

## edition-guide

1 commits in 8e0ec8c77d8b28b86159fdee9d33a758225ecf9c..beea0a3cdc3885375342fd010f9ad658e6a5e09a
2021-11-12 06:30:23 -0800 to 2021-12-05 07:06:45 -0800
- Fix typo (neccesary -> necessary) (rust-lang/edition-guide#274)

Author: matthiaskrgr