Rename flags in aapt2-optimize for more accuracy and consistency.

--enable-resource-path-shortening => --shorten-resource-paths
--enable-resource-obfuscation => --collapse-resource-names

Bug: 140883718
Test: Verified by running `aapt2 optimize
Change-Id: I697713f49b27ccf5f152c76e256234c041dc5f51