PackageManager: Factor out extractNativeLibFromApk()

This will be reused later for running apps in compatiblity mode on
16kB devices -- if extractNativeLibs is false and the libraries are
not 16kB-page-aligned in the zipped apk.

Bug: 339709616
Test: manually install apps
Change-Id: Ifc78525114b99d1076724079e5db78c7e1050d50
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>