AAPT2: normalize Manifest java identifiers.

Currently AAPT2 does not allow permissions which last piece contains the
"-" symbol (since it is an illegal character for a java identifier).

AAPT1 would normalize the last piece, therefore creating a valid java
identifier.

This CL makes AAPT2 behave in a similar way to AAPT1, but instead of
modifying the original value of the permission string, modifies only the
java identifier part, leaving the permission string unchanged.

Fixes: 72980877
Test: updated
Change-Id: Ie44317e07407341ba3e91a84d9b06980547b3448