Add bta/dm/bta_dm_act::BTA_dm_notify_remote_features_complete

Although the connection has been made, subsequent queries
of remote host may not have been completed.  One important
set of data BTA requires is the remote features.

This callback allows synchronization for valid remote
features.

Bug: 163134718
Tag: #refactor
Test: gd/cert/run --host

Change-Id: Icc104e2f47bd79f904a684a7290ca38a123e3cfb