hw/bluetooth.default.so -> libbluetooth.so (2/2)

Also rename the build goal for both the library and headers.

Bug: 67853426
Test: run Bluetooth
Merged-In: I4c2a86fd73da9b4bcad932acc185c844a3c35e3f
Change-Id: I4c2a86fd73da9b4bcad932acc185c844a3c35e3f
(cherry picked from commit 2005718d274ae6668dc3069e4119b08051cbc07a)