Fix auto-config not working issue

issue: e/backlog#5522

Auto-config in release build did not work previously because of:
- strickpolicy disabled in release mode, so network call was not
  possible in main thread
- proguard-rules.pro guard did not has rules for retrofit2 & simpleXml.

This commit does the following:
- Move automatic account creation code under IO thread using kotlin
  coroutine.
- Add new place-holder loading layout for messageList to show when
  loading accounts in the background thread.
- Add missing proguard rules.