Progress towards efficient XML serialization.

Related changes are introducing new TypedXmlSerializer and
TypedXmlPullParser interfaces which offer efficient access to
primitive attributes, and this Error Prone detector helps identify
code that should shift to using those new interfaces.

Bug: 171832118
Test: atest error_prone_android_framework_test
Change-Id: Ic3ca6b96d2b056e6178e407af886bb925a3471c8