refactor(test): migrate Cypress component test to vitest

[susnux]

Summary

Reasons for this:

• Cypress component tests dropped support for Vue 2 long time ago
• Component tests are basically unit tests so we can reduce the unit test frameworks to one (we dropped Karma already)
• Much faster execution time then spinning up a browser
• Most important Cypress does not like component tests with mixed Vue versions, so this is blocking the Vue 3 migration. Because it will try to always use its internal Vue version (Vue 2). So this already breaks updating @nextcloud/dialogs or @nextcloud/password-confirmation which are already using Vue 3.

Other benefits: We can mock whatever we want because its now more like normal unit tests.
So its also a bit easier to test composables etc and only have to think about one way of writing your frontend unit tests located next to your source code.
For real browser tests we have end2end tests which are still Cypress :)

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

[szaimen]

🐘

[susnux]

just for your information this is also somewhat of an a11y fix as per WCAG every fieldset (role group) must have a label by using a legend.