core: Split LE and BR/EDR states for devices

core: Split LE and BR/EDR states for devices

For dual mode devices there are several state variables that are
independent for each bearer. This patch splits these states up into two
separate variable groups in btd_device and tracks the values based on
what kind of connection is in question.

The information is also used to select which bearer to use with
Device1.Connect and Device1.Pair. The basic rule is that the bearer
that's not connected/paired is selected, or then the bearer over which
the device was last seen is selected.