Refactor: Mv OsStr/OsStrExt to core, OsString/OsStringExt to alloc

Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>

Author: NobodyXu

library/Cargo.lock

@@ -28,6 +28,7 @@ dependencies = [
 name = "alloc"
 version = "0.0.0"
 dependencies = [
+ "cfg-if",
  "compiler_builtins",
  "core",
  "rand",

library/alloc/Cargo.toml

@@ -11,6 +11,7 @@ edition = "2021"
 [dependencies]
 core = { path = "../core" }
 compiler_builtins = { version = "0.1.118", features = ['rustc-dep-of-std'] }
+cfg-if = { version = "1.0", features = ['rustc-dep-of-std'] }
 
 [dev-dependencies]
 rand = { version = "0.8.5", default-features = false, features = ["alloc"] }

library/alloc/src/ffi/mod.rs

@@ -89,3 +89,18 @@ pub use self::c_str::{FromVecWithNulError, IntoStringError, NulError};
 
 #[unstable(feature = "c_str_module", issue = "112134")]
 pub mod c_str;
+
+#[stable(feature = "rust1", since = "1.0.0")]
+#[doc(inline)]
+pub use self::os_str::OsString;
+
+#[unstable(feature = "os_str_display", issue = "120048")]
+pub mod os_str;
+
+#[unstable(
+    feature = "os_str_internals",
+    reason = "internal details of the implementation of os str",
+    issue = "none"
+)]
+#[doc(hidden)]
+pub mod wtf8;