[1/2] Base: Speed up booting on multicore devices

- Add multithreading support to Installer/installd
- Parallelize package scanning
- Parallelize boot dexopt

Change-Id: Ia6b815bde0e5cdf996fdfdec3ba228bcde9e4e0b
Merge "[1/2] Base: Speed up booting on multicore devices" into android-4.4