Enable optional codec by default

* Set option codec support/enable status to unknown as their
  default value.
* When a remote Bluetooth device is connected A2DP with optional
  codec selection supported, we should default enable, we should
  enable this feature if the current enable state is unknown.
* Add unit test for this case.

Test: runtest bluetooth
Bug: 124254557
Change-Id: Idc682cd197295c792a45dd0ab2f286d89093e09c