Update submit buttons to use Pajamas component

What does this MR do and why?

Describe in detail what your merge request does and why.

1. Update submit button to use Pajamas component

Screenshots or screen recordings

Before	After

How to set up and validate locally

• Admin > Settings > Preferences > Polling interval multiplier
• Change the value
• Save changes
• Check the changes are saved
• Change the settings back to how they were, unless you want to keep the new values 🤷

2. Update pages settings submit button to use Pajamas component

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Set up the pages feature on a project. The easiest way to do that is:
2. Projects > New project > Create from template > Pages/Plain HTML
3. Finish setting up the project
4. Run the pipeline on master to create you site
5. Project > Settings > Pages > Pages
6. Change the maximum size value
7. Save changes
8. Check the changes are saved
9. Change the settings back to how they were, unless you want to keep the new values 🤷

3. Update welcome submit button to use Pajamas component

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Register for a new account
2. Sign in with new user and see welcome page
3. In app/views/registrations/welcome/show.html.haml comment L38-40 to make othe r button show.
4. Check button still submits

4. Update resend confirmation submit button to use Pajamas component

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Register for a new account
2. Confirm email address using the link sent to user http://127.0.0.1:3000/rails/letter_opener
3. Try and reconfirm using the same link
4. Check button still submits

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.