Rollup merge of #142158 - xizheyin:141617, r=jdonszelmann

Tracking the old name of renamed unstable library features

This PR resolves the first problem of rust-lang/rust#141617 : tracking renamed unstable features. The first commit is to add a ui test, and the second one tracks the changes. I will comment on the code for clarification.

r? `@jdonszelmann`
There have been a lot of PR's reviewed by you lately, thanks for your time!

cc `@jyn514`

compiler/rustc_attr_parsing/src/attributes/stability.rs

@@ -298,6 +298,7 @@ pub(crate) fn parse_unstability<S: Stage>(
     let mut issue_num = None;
     let mut is_soft = false;
     let mut implied_by = None;
+    let mut old_name = None;
     for param in args.list()?.mixed() {
         let Some(param) = param.meta_item() else {
             cx.emit_err(session_diagnostics::UnsupportedLiteral {
@@ -345,11 +346,12 @@ pub(crate) fn parse_unstability<S: Stage>(
             Some(sym::implied_by) => {
                 insert_value_into_option_or_error(cx, &param, &mut implied_by)?
             }
+            Some(sym::old_name) => insert_value_into_option_or_error(cx, &param, &mut old_name)?,
             _ => {
                 cx.emit_err(session_diagnostics::UnknownMetaItem {
                     span: param.span(),
                     item: param.path().to_string(),
-                    expected: &["feature", "reason", "issue", "soft", "implied_by"],
+                    expected: &["feature", "reason", "issue", "soft", "implied_by", "old_name"],
                 });
                 return None;
             }
@@ -374,6 +376,7 @@ pub(crate) fn parse_unstability<S: Stage>(
                 issue: issue_num,
                 is_soft,
                 implied_by,
+                old_name,
             };
             Some((feature, level))
         }