Use Pajamas button component for form submit

What does this MR do and why?

Based on the epic description, this migrates form submits in our Haml to use the component, instead of repeating the same CSS classes on every = form.submit.

How to set up and validate locally

Ensure that the submit buttons under the following are still functional and use the confirm (blue) button variant. Replace the start of the path with your local one:

• /admin/application_settings/preferences under the Gitaly timeouts section
• /admin/application_settings/metrics_and_profiling#js-sentry-settings under the Sentry section
  • Enable the Sentry control feature

    Feature.enable(:configure_sentry_in_application_settings)

• /admin/deploy_keys add a new deploy key
• /-/profile/gpg_keys
• /-/profile/emails

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.

Closes #374802 (closed), #374801 (closed), #374803 (closed), #374804 (closed), #374805 (closed)