Use ToString specialization macro also for Cow and String

Author: tbu-

library/alloc/src/string.rs

@@ -2966,6 +2966,8 @@ macro_rules! to_string_str {
 
 #[cfg(not(no_global_oom_handling))]
 to_string_str! {
+    Cow<'_, str>,
+    String,
     // Generic/generated code can sometimes have multiple, nested references
     // for strings, including `&&&str`s that would never be written
     // by hand.
@@ -2984,22 +2986,6 @@ to_string_str! {
     str,
 }
 
-#[cfg(not(no_global_oom_handling))]
-impl SpecToString for Cow<'_, str> {
-    #[inline]
-    fn spec_to_string(&self) -> String {
-        self[..].to_owned()
-    }
-}
-
-#[cfg(not(no_global_oom_handling))]
-impl SpecToString for String {
-    #[inline]
-    fn spec_to_string(&self) -> String {
-        self.to_owned()
-    }
-}
-
 #[cfg(not(no_global_oom_handling))]
 impl SpecToString for fmt::Arguments<'_> {
     #[inline]