Rollup merge of rust-lang#132579 - RalfJung:rustc-std-workspace-crate…

…s, r=Amanieu

add rustc std workspace crate sources

This adds the sources for the crates listed at https://crates.io/search?q=rustc-std-workspace in this repo. The first commit adds the original sources as downloaded from crates.io (with `Cargo.toml.orig` moved back over `Cargo.toml`), and adds a README explaining what this is about. The 2nd commit updates the sources to make the core and alloc crates re-exports of the "actual" core and alloc crates, as was already the case with `std`, and also adds a `repository` link to the manifest so one can figure out where to find these crates.

I bumped the version for the core and alloc crates in the hope that the new versions can be published on crates.io shortly after this PR lands.

See [Zulip](https://rust-lang.zulipchat.com/#narrow/channel/219381-t-libs/topic/rustc-std-workspace-core.20crate.20is.20empty) for a bit more context.

r? `@Amanieu`

rustc-std-workspace-core/README.md

@@ -27,3 +27,6 @@ it'll look like
 
 when Cargo invokes the compiler, satisfying the implicit `extern crate core`
 directive injected by the compiler.
+
+The sources for the crates.io version can be found in
+[`src/rustc-std-workspace`](../../src/rustc-std-workspace).