Describe the bug
When a survey has a lot of response (400 or more for example), it can take 15 seconds to display the survey page.

To Reproduce
Steps to reproduce the behavior:

1. Create a survey with multiple questions
2. Fill in the survey (if possible hundreds of answers)
3. Goto the page of the survey (either authenticated or not)
4. The survey will take a long time to display

Expected behavior
Response time should be irrelevant of the number of responses to the survey.

Screenshots
N/A

Stacktrace
If applicable, add the error stacktrace to help explain your problem.

Extra data (please complete the following information):

• Device: Desktop
• Device OS: All OS
• Browser: Any browser
• Decidim Version: 0.18.0
• Decidim installation: Ansible

Additional context
Running a debug while displaying the page, we can see a lot of requests to the server before displaying the page. It looks like all current answers are queried before displaying the page to answer the survey:

D, [2020-02-10T12:21:06.823281 #101275] DEBUG -- : [be64942f-dfd4-4e5a-8671-41ec91a35479]   CACHE Decidim::Forms::Question Load (0.0ms)  SELECT  "decidim_forms_questions".* FROM "decidim_forms_questions" WHERE "decidim_forms_questions"."id" = $1 LIMIT $2  [["id", 61], ["LIMIT", 1]]
D, [2020-02-10T12:21:06.827444 #101275] DEBUG -- : [be64942f-dfd4-4e5a-8671-41ec91a35479]   Decidim::Forms::AnswerChoice Load (2.1ms)  SELECT "decidim_forms_answer_choices".* FROM "decidim_forms_answer_choices" WHERE "decidim_forms_answer_choices"."decidim_answer_id" = $1  [["decidim_answer_id", 2200]]

...
repeated hunderds of times