fix(test): fix initialization order in Test_Parser

Parser's constructor might use the diag reporter (because
Parser::Parser calls Lexer::Lexer which lexes the first token). Ensure
Test_Parser's diag reporter is initialized before making the Parser.

test/quick-lint-js/parse-support.h

@@ -185,14 +185,14 @@ class Test_Parser {
                           Source_Location caller);
 
  private:
+  Monotonic_Allocator diag_allocator_{"Test_Parser::diag_allocator_"};
+  Diag_List_Diag_Reporter diag_reporter_{&this->diag_allocator_};
+
   Padded_String code_;
   Spy_Visitor errors_;
   Failing_Diag_Reporter failing_reporter_;
   quick_lint_js::Parser parser_;
 
-  Monotonic_Allocator diag_allocator_{"Test_Parser::diag_allocator_"};
-  Diag_List_Diag_Reporter diag_reporter_{&this->diag_allocator_};
-
  public:
   // Aliases for convenience.
   std::vector<std::string_view>& visits = this->errors_.visits;