Don't depend on annotation processors XmlWriter.

The annotation processor is being modified to produce an intermediate
output that will then be processed to produce the config that ends up on
device. As such, using XmlWriter in frameworks test code no longer makes
sense.

Instead, hard-code XML config in the test to break this problematic
dependency.

Test: atest CompatConfigTest
Change-Id: I371ba32bd83d6a84de94d594169dbb5c63f3d9be
Merged-In: I371ba32bd83d6a84de94d594169dbb5c63f3d9be