DO NOT MERGE: Do not allow overlaying of attributes with conflicting formats

aapt(1) does not allow for attributes to be redefined with a different
format. Also, attributes declared with enums or flags are never allowed to be
redefined. This change will not allow attributes to be redefined with a
conflicting format in aapt2.

Bug: 129146717
Test: aapt2_tests
Change-Id: Idc43d6d689199ba2cdc672d009ede22eaa75a10c