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.

(cherry picked from commit 96ea08f1)

Also includes part of I357fb84941bfbb3892a8c46feb47f55b865b6649 to remove
usage of FindNonAlphaNumericAndNotInSet.

Bug: 79481102
Test: make aapt2_tests
Change-Id: I1052e9e82b6617db6065ce448d9bf7972bb68d59
Merged-In: I1052e9e82b6617db6065ce448d9bf7972bb68d59