[Feature]: Merge "add contact" and "contact requests" views

[tmolitor-stud-tu]

Precondition

• I understood that this template is only for feature requests and not for bug reports

Cross-checked related issues?

• I have cross-checked this overview Overview: Tasks and Issues #322 as well as filtered for related labels https://github.com/monal-im/Monal/labels

Describe your feature

Merge "add contact" and "contact requests" views for better UX.

Show the current add contact view below the current contact requests view if there are any open contact requests. If there are none, reverse that order.