Rollup merge of #134851 - lukas-code:alloc-ffi, r=tgross35

docs: inline `alloc::ffi::c_str` types to `alloc::ffi`

like #134791 but for `alloc`

r? ``@tgross35`` ``@notriddle``

Author: Zalathar

library/alloc/src/ffi/mod.rs

@@ -83,7 +83,7 @@
 #[doc(inline)]
 #[stable(feature = "alloc_c_string", since = "1.64.0")]
 pub use self::c_str::CString;
-#[doc(no_inline)]
+#[doc(inline)]
 #[stable(feature = "alloc_c_string", since = "1.64.0")]
 pub use self::c_str::{FromVecWithNulError, IntoStringError, NulError};