adapt to last-minute instant-onboarding changes

[bjoern]

deltachat/deltachat-android#3060, deltachat/deltachat-android#3064, deltachat/deltachat-android#3068 are the outcome of one-to-one discussions during the current gathering; see there fore reasoning and discussion.

in summary, the following changes are needed in onboarding:

• pull translations
• create a regular secondary button with the string Use Other Server (instant_onboarding_show_more_instances) below "Agree & Create Profile"
• on tapping Use Other Server, an dialog (same as for "I already have a login") with the following options should open:
  • List Chatmail Servers (instant_onboarding_other_server) - do the same as "Explore Other Options" before
  • Classic E-Mail Login (manual_account_setup_option) - do the same as "I Already Have A Login / Manual Login" before
  • Scan Invitation Code (scan_invitation_code) - do the same a "Scan QR Code" before
• remove the lower two buttons "Explore Other Options" and "Scan QR Code"
• remove "I Already Have A Login / Manual Login" (options left are "Add as Second Device" and "Restore From Backup")

the following changes are needed in "New Chat":

• rename "Scan QR Code" to New Contact (menu_new_contact) and move it up
• if isChatmail() is true, the placeholder must no longer read "Enter name or e-mail address" but just Search (search)
• if an email address is entered, rename "New Contact" to Add Contact Manually (menu_new_classic_contact)

(showing it unconditional to isChatmail() seems to be the easiest option, gist is that when isChatmail() is true, there is no easy path to enter an email address (alternatives would be deltachat/deltachat-android#3064 , but that would require a menu in the "QR Code" dialog and may be harder)

in manual contact adding activity:

• use the title Add Contact Manually (menu_new_classic_contact)
• add the hint new_classic_contact_explain below the input fields