Refactor Typeface construction logic

API refactoring:
- Replace Font.getWeight()/getSlant() with Font.getStyle().
- Change Typeface.CustomFallbackBuilder.setItalic() to setSlant()

Implementation refactoring:
- Add hidden builder API for asset manager with cookie. The cookie is
internal, so hide the API as well.
- Replace createFromResources with Typeface.Builder
- Reimplement Typeface.Builder with Typeface.CustomFallbackBuilder

Ground work for b/114479228
- Keep list of FontFamily in the Typeface.

Bug: 114479228
Test: atest CtsTestCases
Test: atest CtsGraphicsTestCases
Test: atest CtsWidgetTestCases
Change-Id: Ifaaa58ddea147644a93158aa075394c2f645617c