Improve compliance frameworks form UI/UX

While developing the add and edit compliance framework forms, there have been a few points noted as to improvements we could make on the overall UI text and UX.

1. The add forms submit button should say "Add framework" not "Save changes"
2. On successful submission of the form, the form should not be reshown while waiting for the redirection to take place
3. The success banner on the listing is marked as dismissable but doesn't actually dismiss: !54224 (comment 515680449)

Tier

The ability to create/edit/assign custom compliance labels is a GitLab Ultimate feature.

Feature flag

This feature should only be shown if the feature flag :ff_custom_compliance_frameworks is set

Implementation plan

TBD