重构 problem 和 contest；修改测试和部分模板的结构

contest_submission/views.py

@@ -76,7 +76,7 @@ def contest_problem_my_submissions_list_page(request, contest_id, contest_proble
     submissions = Submission.objects.filter(user_id=request.user.id, problem_id=contest_problem.id).order_by(
         "-create_time"). \
         values("id", "result", "create_time", "accepted_answer_time", "language")
-    return render(request, "oj/contest/my_submissions_list.html",
+    return render(request, "oj/submission/problem_my_submissions_list.html",
                   {"submissions": submissions, "problem": contest_problem})