[Direct Message] Enhance discovery result section

[giomfo]

When the user provides an email address in the new direct message screen, Element-Android displays a discovery result when the consent has been granted.

• Rename the section "Discovery" with "Utilisateur découvert", and remove/hide the id server url.
• In tchapV2, we decide to change the suggested action when no Tchap account has been found
  
  "Inviter par email" should create a DM with this email address (like the other case of invite in Tchap via email). The resulting DM will be hidden until the email owner creates their account. A toast is displayed to notify the user

[giomfo]

tested ok