Standardize dropdown-menu heights

[Dassderdie]

The Problem(s)

Start an exercise with many hospitals/transfer points/viewports/.... (e.g. https://github.com/hpi-sam/digital-fuesim-manv_test-scenarios/blob/19cca04a673dc5a2aa09ddf42aac174cbf54144e/exercise-state-2022-05-31-workshop-babz-gro%C3%9Fes-szenario.json)

1. The heights of some dropdown menus are too small (user feedback).
   

2. In the opinion of @Dassderdie, all dropdowns should have a maximum height (200px or 250px).

Current	Wanted

Solution Hints

• Remove all custom heights from every ngbDropdownMenu (https://ng-bootstrap.github.io/#/components/dropdown/examples)
• Add a global style in frontend\src\styles.scss
  • https://developer.mozilla.org/en-US/docs/Web/CSS/max-height
  • https://developer.mozilla.org/en-US/docs/Web/CSS/overflow