Make account and application dropdown scrollable

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## Feature request

**Which Nextcloud Version are you currently using:** (see administration page)
Windows nextcloud client 4.0.6.

**Is your feature request related to a problem? Please describe.**
If you have a lot of nextcloud accounts and a lot of installed applications, the visible lists of the dropdowns get exhausted. You can't access all of them! In case of account dropdown, its not possible to add an additional account.

**Describe the solution you'd like**
Make both dropdowns scrollable.

**Describe alternatives you've considered**
Make application window resizable.

**Additional context**