feat(ast): tie debug_name return lifetime to the underlying AST node (#27295)

Return Cow<'a, str> instead of tying the result to the borrow of
the AstKind wrapper. This lets callers retain a debug name obtained
from a temporary AstKind while the underlying AST node remains alive.

The longer lifetime is sound: AstKind<'a> holds node references valid
for 'a, and every returned value is either an owned string, a static
string, or directive text borrowed from storage valid for 'a.

Co-authored-by: Cameron <cameron.clark@hey.com>

crates/oxc_ast/src/ast_kind_impl.rs

@@ -362,13 +362,13 @@ impl<'a> AstKind<'a> {
     }
 }
 
-impl AstKind<'_> {
+impl<'a> AstKind<'a> {
     /// Get the AST kind name with minimal details. Particularly useful for
     /// when debugging an iteration over an AST.
     ///
     /// Note that this method does not exist in release builds. Do not include
     /// usage of this method within your code.
-    pub fn debug_name(&self) -> std::borrow::Cow<'_, str> {
+    pub fn debug_name(&self) -> std::borrow::Cow<'a, str> {
         use std::borrow::Cow;
 
         const COMPUTED: &str = "<computed>";