zipalign: Allow specifiying the target page size

Allow apps to specify the target page size for aligning their
uncompressed shared libraries.

This allows apps that want to support larger page sizes to do
so by specifiying the -P <pagesize_kb> flag.

However, apps built for 4k-only devices are unaffected as they
can continue to use -p flag for 4kB page alignment of uncompressed
shared libraries.

Bug: 276963821
Test: atest -c zipalign_tests
Change-Id: I890db067b8f898045f73e86788662f94a48af772
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>