vndk-def: Simplify VNDK result

This commit adds extra_vendor_libs and removes extra_vndk_sp_indirect.
With this modification, we can tag each libraries with either vndk_ext,
extra_vendor_libs, vndk_sp_ext or vndk_sp_indirect_ext.

After tagging them precisely, we merge them into vndk_sp, vndk_sp_ext
and extra_vendor_libs before printing the simplified VNDK list.  This
will give us accurate tags when --full is specified and give concise
tags when --full is not specified.

Bug: 37867089
Test: 3 essential sets are printed when --full was not specified.
Change-Id: Ic17c5e1dd4420050217e9724f86516c21609f899