Rollup merge of #80523 - LeSeulArtichaut:inline-sym, r=jyn514

#[doc(inline)] sym_generated

Manually doc-inlines `rustc_span::sym_generated` into `sym`.
Previously the docs would not get inlined, causing the symbols to be undocumented as `sym_generated` is private.

r? `@jyn514`

compiler/rustc_span/src/symbol.rs

@@ -1604,6 +1604,7 @@ pub mod sym {
     use super::Symbol;
     use std::convert::TryInto;
 
+    #[doc(inline)]
     pub use super::sym_generated::*;
 
     // Used from a macro in `librustc_feature/accepted.rs`