fix(AdminSettings): hide secrets in password fields

[ShGKme]

☑️ Resolves

• A part of: Adjust UI according to the design review #12800

🖌️ UI Checklist

🖼️ Screenshots / Screencasts

🏚️ Before	🏡 After
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🚧 Tasks

• Replace Text fields with password fields for shared secrets
• Add autocomplete="new-password" to not save the password
  • Completely disable is not possible with type="password", forced by web-browsers
• Add names just in case, so browsers and tools may know these are not user passwords and are different values

🏁 Checklist

• 🌏 Tested with Chrome, Firefox and Safari or should not be risky to browser differences
• 🖥️ Tested with Desktop client or should not be risky for it
• 🖌️ Design was reviewed, approved or inspired by the design team
• ⛑️ Tests are included or not possible
• 📗 User documentation in https://github.com/nextcloud/documentation/tree/master/user_manual/talk has been updated or is not required

[ShGKme]

/backport to stable29

[ShGKme]

/backport to stable28