HFP: Save discovered HFP version to config file

* Store discovered HFP version to btif config file so that a
  reconnection session knows the HFP version before SDP
* Check stored HFP version when RFCOMM channel is open before any AT
  command is processed
* Set peer HFP version to 0 on control block allocation

Bug: 67938255
Test: Connect with HFP 1.7 headsets
Change-Id: I43e7aa04dee17ea7ba9e7d3992ec0860c11d23bc