Use UITextView to calculate the message height

[SystemKeeper]

We discovered some height calculation issues depending on font size, text and used iOS device.

We also tried to move back to

let boundingRect = messageString.boundingRect(with: container.size, options: [.usesLineFragmentOrigin, .usesFontLeading], context: nil)

But this did also not work properly and sometimes text was missing from the text.