AAPT2: Differentiate between Android and Java package names

Android package names are more strict (ASCII only) than Java package names.
Also fixed an issue where trailing underscores were disallowed in Android
package names.

Bug: 68468089
Test: make aapt2_tests
Change-Id: I1052e9e82b6617db6065ce448d9bf7972bb68d59
6 files changed