Stop confetti popup from opening on browser back button

What does this MR do and why?

• keeps the confetti popup modal from opening on browser back button
• switches from rails session cookies to regular cookies so they can be referenced in javascript that is re-rendered on page load.

Screenshots or screen recordings

no modal popup when back button used

Screen_Recording_2022-02-10_at_3.25.52_PM

How to set up and validate locally

1. Enable the confetti_post_signup

   Feature.enable(:confetti_post_signup)

2. Register as a new user by visiting http://localhost:3000/users/sign_up(or by clicking Register now from http://localhost:3000/users/sign_in)

3. Answer Just me on the http://localhost:3000/users/sign_up/welcome page(no other fields need filled out/changed)

4. Click Continue

5. On the next few screens, fill out new Group and Project names.

6. Wait for the Get Started with GitLab to finish.

7. Click Ok, let's go.

8. Observe invite modal open on next screen.

9. Close the modal.

10. Click a link on the page.

11. Click the browser back button.

12. Ensure modal doesn't open again.(before this change it did)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.