Convert group authentication checkox to toggle button

What does this MR do?

This MR updates the enable group auth checkbox to a toggle button

before	after

What are the relevant issue numbers?

#9406 (closed)

How to test this change locally

You need to add the below to your config/gitlab.yml file

providers:
  - { name: 'group_saml' }

You'll also have to run Feature.enable(:group_scim) via the Ruby console in order to enable the feature flag.

Then select a group -> hover settings -> select SAML SSO

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the style guides
• EE specific content should be in the top level /ee folder