AAPT2: treat manifest validation errors as warnings when asked

Bug: 65670329
Test: updated
Change-Id: Ic554cc20134fce66aa9ddf8d16ddffe0131c50e9
Merged-In: Ic554cc20134fce66aa9ddf8d16ddffe0131c50e9
(cherry picked from commit ad9e1324ff2c459d0ee6ee571d4a3e458c02cc81)
6 files changed