rename stable_mir to rustc_public, and rustc_smir to rustc_public_bridge

Author: makai410

compiler/rustc_public/README.md

@@ -0,0 +1,46 @@
+This crate is currently developed in-tree together with the compiler.
+
+Our goal is to start publishing `stable_mir` into crates.io.
+Until then, users will use this as any other rustc crate, by installing
+the rustup component `rustc-dev`, and declaring `stable-mir` as an external crate.
+
+See the StableMIR ["Getting Started"](https://rust-lang.github.io/project-stable-mir/getting-started.html)
+guide for more information.
+
+## Stable MIR Design
+
+The stable-mir will follow a similar approach to proc-macro2. Its
+implementation is split between two main crates:
+
+- `stable_mir`: Public crate, to be published on crates.io, which will contain
+the stable data structure as well as calls to `rustc_smir` APIs. The
+translation between stable and internal constructs will also be done in this crate,
+however, this is currently implemented in the `rustc_smir` crate.[^translation].
+- `rustc_smir`: This crate implements the public APIs to the compiler.
+It is responsible for gathering all the information requested, and providing
+the data in its unstable form.
+
+[^translation]: This is currently implemented in the `rustc_smir` crate,
+but we are working to change that.
+
+I.e.,
+tools will depend on `stable_mir` crate,
+which will invoke the compiler using APIs defined in `rustc_smir`.
+
+I.e.:
+
+```
+    ┌──────────────────────────────────┐           ┌──────────────────────────────────┐
+    │   External Tool     ┌──────────┐ │           │ ┌──────────┐   Rust Compiler     │
+    │                     │          │ │           │ │          │                     │
+    │                     │stable_mir| │           │ │rustc_smir│                     │
+    │                     │          │ ├──────────►| │          │                     │
+    │                     │          │ │◄──────────┤ │          │                     │
+    │                     │          │ │           │ │          │                     │
+    │                     │          │ │           │ │          │                     │
+    │                     └──────────┘ │           │ └──────────┘                     │
+    └──────────────────────────────────┘           └──────────────────────────────────┘
+```
+
+More details can be found here:
+https://hackmd.io/XhnYHKKuR6-LChhobvlT-g?view

compiler/rustc_public/rust-toolchain.toml

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+[toolchain]
+channel = "nightly-2023-06-14"
+components = [ "rustfmt", "rustc-dev" ]