Add search / filtering for the create chat view

[Boehrsi]

Is your feature request related to a problem? Please describe.
The user should be able to filter / search for contacts in the create chat view.

Describe the solution you'd like

• Use the given designs
• Performing a search should use given DCC functions https://c.delta.chat/classdc__context__t.html#a32f1458afcacf034148952305bf60abe
• A list of results should be shown / the list should get filtered
• Tapping opens a new chat with the contact

Internal Bug Tracker