Auto merge of #58623 - Amanieu:hashbrown3, r=alexcrichton

Replace HashMap implementation with SwissTable (as an external crate)

This is the same as #56241 except that it imports `hashbrown` as an external crate instead of copying the implementation into libstd.

This includes a few API changes (all unstable):
- `try_reserve` is added to `HashSet`.
- Some trait bounds have been changed in the `raw_entry` API.
- `search_bucket` has been removed from the `raw_entry` API (doesn't work with SwissTable).

src/tools/rustc-std-workspace-alloc/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "rustc-std-workspace-alloc"
+version = "1.0.0"
+authors = ["Alex Crichton <alex@alexcrichton.com>"]
+license = 'MIT/Apache-2.0'
+description = """
+Hack for the compiler's own build system
+"""
+
+[lib]
+path = "lib.rs"
+
+[dependencies]
+alloc = { path = "../../liballoc" }

src/tools/rustc-std-workspace-alloc/lib.rs

@@ -0,0 +1,9 @@
+#![feature(no_core)]
+#![no_core]
+
+// See rustc-std-workspace-core for why this crate is needed.
+
+// Rename the crate to avoid conflicting with the alloc module in liballoc.
+extern crate alloc as foo;
+
+pub use foo::*;