Mechanical refactoring to new XML resolvers.

Related changes are introducing new TypedXmlSerializer and
TypedXmlPullParser interfaces which offer efficient access to
primitive attributes.

This change is a purely mechanical refactoring to prepare for
upcoming data format shifts, and has no behavior changes.

Bug: 171832118
Test: manual
Exempt-From-Owner-Approval: trivial no-op refactoring
Change-Id: Ib8045ddba489c254641d6331b64355709c3f6dd7