Show a "Verify" button under the Encryption Enabled banner

**Is your feature request related to a problem? Please describe.**
Finding the verification starting button is hard for non-techie users (given that the settings screen for DMs is the same for groups, but they aren't familiar with this concept from other messenger platforms).

**Describe the solution you'd like**
If there is only 2 participants in the chat, the Encryption Enabled banner should have a "Verify" button, similarly like the "Incoming verification request" banner has the "Reject" and "Accept" button.