Read OEM customization XML

We now moved OEM font customization outside of system image and all
system font modifications are in /product directory.

In this CL, only customizationType="new-named-family" is supported.

My previous CL If58711fc038898175fcad0ae095865312bd738e2 breaks test
cases in CtsGraphicsTestCases but TreeHugger didn't catch my mistake
becasue the test cases are not annotated as Presubmit.

Bug: 111544833
Test: atest CtsGraphicsTestCases:android.graphics.fonts
Change-Id: I7a7a2d91d8f37c51944d598dde7562733eae5626