Implement system namespace for vendor process

For vendor process default namespace searches as following order:
1. /vendor/lib/(hw|egl), /vendor/lib: Vendor libs + VNDK-vnd-ext
2. /system/lib/vndk-$(ver): VNDK libs
3. /vendor/lib/vndk-sp-$(ver): VNDK-SP-vnd-ext
4. /system/lib/vndk-sp-$(ver): VNDK-SP
and searches system namespace (/system/lib) only for LL-NDK libs.
This configuarion is used only with BOARD_VNDK_VERSION is defined.

Bug: 37192038
Test: build with 'BOARD_VNDK_VERSION=current' and boot

Change-Id: If9778b9266a084846ba8fe73e6bff25828359d33