cue/ast/astutil: stop using the deprecated ast.ParseIdent

Quoted identifiers haven't been supported or used for years.
https://cuelang.org/cl/531206 dropped support for them entirely,
but missed updating the astutil package accordingly.

Since ParseIdent works on the Name field, and quoted identifiers
are no longer supported, we can use the Name field directly as-is.

Signed-off-by: Daniel Martí <mvdan@mvdan.cc>
Change-Id: I64e470865bffdc3d97290a50389a9d60878c7ea6
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1185683
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>
Reviewed-by: Paul Jolly <paul@myitcv.io>
TryBot-Result: CUEcueckoo <cueckoo@gmail.com>

cue/ast/astutil/resolve.go

@@ -308,10 +308,7 @@ func (s *scope) Before(n ast.Node) (w visitor) {
 				// illegal name clashes, and it allows giving better error
 				// messages. This puts the burden on clients of this library
 				// to detect illegal usage, though.
-				name, err := ast.ParseIdent(a.Ident)
-				if err == nil {
-					s.insert(name, a.Expr, a)
-				}
+				s.insert(a.Ident.Name, a.Expr, a)
 			}
 
 			ast.Walk(expr, nil, func(n ast.Node) {
@@ -420,23 +417,14 @@ func scopeClauses(s *scope, clauses []ast.Clause) *scope {
 			walk(s, x.Source)
 			s = newScope(s.file, s, x, nil)
 			if x.Key != nil {
-				name, err := ast.ParseIdent(x.Key)
-				if err == nil {
-					s.insert(name, x.Key, x)
-				}
-			}
-			name, err := ast.ParseIdent(x.Value)
-			if err == nil {
-				s.insert(name, x.Value, x)
+				s.insert(x.Key.Name, x.Key, x)
 			}
+			s.insert(x.Value.Name, x.Value, x)
 
 		case *ast.LetClause:
 			walk(s, x.Expr)
 			s = newScope(s.file, s, x, nil)
-			name, err := ast.ParseIdent(x.Ident)
-			if err == nil {
-				s.insert(name, x.Ident, x)
-			}
+			s.insert(x.Ident.Name, x.Ident, x)
 
 		default:
 			walk(s, c)