[bt][gap] Initiate auto-connect on undirected advertisements

We now process both directed and undirected connectable advertisements
when deciding to auto-connect to a bonded peer. This is consistent with
the "Auto Connection Establishment Procedure" behavior described in v5.1
Vol 3, Part C, 9.3.5.1.

Bug: BT-800 #done
Test: 1. bt-host-unittests
      2. Auto-connecting to a Microsoft Designer Mouse should succeed
         all the time.
Change-Id: Ied65930588085ff48eb8b15af7f82decd7954ad8