install docs for each target in different directory

Solves rust-lang#140922

Rollup of 3 pull requests

Successful merges:

 - #142478 (install docs for each target in different directory)
 - #142629 (Add config builder for bootstrap tests)
 - #142699 (Update books)

Failed merges:

 - #142637 (Remove some glob imports from the type system)

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

install docs for each target in different directory

Solves rust-lang#140922

Rollup of 10 pull requests

Successful merges:

 - #138291 (rewrite `optimize` attribute to use new attribute parsing infrastructure)
 - #141990 (Implement send_signal for unix child processes)
 - #142331 (Add `trim_prefix` and `trim_suffix` methods for both `slice` and `str` types.)
 - #142478 (install docs for each target in different directory)
 - #142571 (Reason about borrowed classes in CopyProp.)
 - #142668 (vec_deque/fmt/vec tests: remove static mut)
 - #142687 (Reduce uses of `hir_crate`.)
 - #142690 (expand: Remove some unnecessary generic parameters)
 - #142699 (Update books)
 - #142714 (add comment to `src/bootstrap/build.rs`)

Failed merges:

 - #142502 (rustdoc_json: improve handling of generic args)

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

install docs for each target in different directory

Solves rust-lang#140922

Rollup of 11 pull requests

Successful merges:

 - #142478 (install docs for each target in different directory)
 - #142629 (Add config builder for bootstrap tests)
 - #142715 (correct template for `#[align]` attribute)
 - #142720 (De-dup common code from `ExternalCrate` methods)
 - #142736 (add issue template for rustdoc)
 - #142743 (rustc-dev-guide subtree update)
 - #142744 (Add a mailmap entry for y21)
 - #142758 (Make sure to rebuild rustdoc if `src/rustdoc-json-types` is changed)
 - #142764 (Convert `ilog(10)` to `ilog10()`)
 - #142767 (Some symbol and PathRoot cleanups)
 - #142769 (remove equivalent new method on context)

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

install docs for each target in different directory

Fixes: #140922

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try-job: dist-i686-msvc