Move Bluetooth off the product="..." strings xml feature

Do a runtime-lookup of the ro.build.characteristics and check for
the nosdcard characteristic instead. This makes the Bluetooth
compile identically, regardless of characteristic (the strings
that didn't apply previously got stripped at compile-time).

Bug: 118618261
Test: tested a failed Bluetooth transfer on a nosdcard device
Change-Id: I59e8b90d3416c96008ea202bb88b61dbce6cfe64