AAPT2: Convert from Modified UTF-8 ResStringPool

Since ResStringPools are encoded using Modified UTF-8, retrieving
strings from the string pool convert the strings to UTF-8 before
returning.

Bug: 114734350
Test: m aapt2_tests
Change-Id: Ib459018186f4c5b40f3f3786425a335ecfb9ed02
3 files changed