Auto merge of #129687 - Urgau:rfc3127-sysroot-2, r=jieyouxu

Implement RFC3137 trim-paths sysroot changes - take 2

This PR is a continuation of rust-lang/rust#118149. Nothing really changed, except for rust-lang/rust#129408 which I was able to trigger locally.

Original description:

> Implement parts of #111540
>
> Right now, backtraces into sysroot always shows /rustc/$hash in diagnostics, e.g.
>
> ```
> thread 'main' panicked at 'hello world', map-panic.rs:2:50
> stack backtrace:
>    0: std::panicking::begin_panic
>              at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/std/src/panicking.rs:616:12
>    1: map_panic::main::{{closure}}
>              at ./map-panic.rs:2:50
>    2: core::option::Option<T>::map
>              at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/core/src/option.rs:929:29
>    3: map_panic::main
>              at ./map-panic.rs:2:30
>    4: core::ops::function::FnOnce::call_once
>              at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/core/src/ops/function.rs:248:5
> note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
> ```
>
> [RFC 3127 said](https://rust-lang.github.io/rfcs/3127-trim-paths.html#changing-handling-of-sysroot-path-in-rustc)
>
> > We want to change this behaviour such that, when rust-src source files can be discovered, the virtual path is discarded and therefore the local path will be embedded, unless there is a --remap-path-prefix that causes this local path to be remapped in the usual way.
>
> This PR implements this behaviour. When `rust-src` is present at compile time, rustc replaces /rustc/$hash with a real path into local rust-src with best effort. To sanitise this, users must explicitly supply `--remap-path-prefix=<path to rust-src>=foo`.

cc `@cbeuw`
Fix #105907
Fix #85463

try-job: dist-x86_64-linux
try-job: x86_64-msvc
try-job: dist-x86_64-msvc
try-job: armhf-gnu