sqlparser: remove strings.Clone from NewIdentifierCS (#19683)

Author: arthurschreiber

go/vt/sqlparser/ast_funcs.go

@@ -1084,11 +1084,7 @@ func (node *IdentifierCI) UnmarshalJSON(b []byte) error {
 
 // NewIdentifierCS creates a new IdentifierCS.
 func NewIdentifierCS(str string) IdentifierCS {
-	// Use StringClone on the table name to ensure it is not pinned to the
-	// underlying query string that has been generated by the parser. This
-	// could lead to a significant increase in memory usage when the table
-	// name comes from a large query.
-	return IdentifierCS{v: strings.Clone(str)}
+	return IdentifierCS{v: str}
 }
 
 // IsEmpty returns true if TabIdent is empty.