The recent PR rust-lang#110688 added info about an item's kind before its name in
search results. However, because the kind and name are inline with no
alignment, it's now hard to visually scan downward through the search
results, looking at item names. This PR fixes that by horizontally
aligning search results such that there are now two columns of
information.

This was added in rust-lang/compiler-builtins#526 to force all
compiler-builtins intrinsics to use weak linkage.

This makes "existential type" look slightly cramped (though still
readable), but it makes all other typenames look better. Existential
types are currently very rare, and we can always tweak this later if
necessary.

almost no one on windows builds from source unless they're contributing,
and `./x.py` just works on most unix systems.

Before:

```
PS C:\Users\vboxuser\rust> ./x
x.ps1

PS C:\Users\vboxuser\rust>
```

After:
```
PS C:\Users\vboxuser\rust> ./x
x.ps1

C:\Users\vboxuser\rust\x.ps1 : C:\Users\vboxuser\rust\x.ps1: error: did not find python installed
help: consider installing it from https://www.python.org/downloads/windows/
At line:1 char:1
+ ./x
+ ~~~
    + CategoryInfo          : NotInstalled: (:) [Write-Error], WriteErrorException
    + FullyQualifiedErrorId : Microsoft.PowerShell.Commands.WriteErrorException,x.ps1
```

The existing message from the shell script is already decent and I decided not to change it:
```
$ ./x
Python was not found but can be installed from the Microsoft Store: ms-windows-store://pdp/?productid=9NJ46SX7X90P
```

This is left over from adding `Get-Command -syntax`; it's not helpful.

…le,GuillaumeGomez

rustdoc: Align search results horizontally for easy scanning

The recent PR rust-lang#110688 added info about an item's kind before its name in
search results. However, because the kind and name are inline with no
alignment, it's now hard to visually scan downward through the search
results, looking at item names. This PR fixes that by horizontally
aligning search results such that there are now two columns of
information.

r? `@GuillaumeGomez`

DirEntry::file_name: improve explanation

…mulacrum

Expose `compiler-builtins-weak-intrinsics` feature for `-Zbuild-std`

This was added in rust-lang/compiler-builtins#526 to force all compiler-builtins intrinsics to use weak linkage.

…s, r=clubby789

Move some docs from the README to the dev-guide

and as a drive-by cleanup, improve the error message for `x test tidy` when a feature gate is missing.

This also improves the error message you get on Windows if python isn't installed.

cc rust-lang/libs-team#242 (comment), rust-lang/rustc-dev-guide#1701

…jubilee

Remove unnecessary `path` attribute

Follow up to rust-lang#111401. I missed this at the time but it should now be totally unnecessary since the other include was removed.

r? `@workingjubilee`