Consolidate getFamilyAt() calls to minikin.

- Typeface: Use FontCollection::createCollectionWithFamilies() instead
  of creating fallback list inside hwui.
- system_fonts: Use SystemFonts::getFontSet() intead of getFontMap().

Bug: 174672300
Test: atest CtsGraphicsTestCases:android.graphics.cts.TypefaceTest
Test: atest CtsGraphicsTestCases:android.graphics.fonts.NativeSystemFontTest
Change-Id: I940f8de441b7bd102eca2d08bc5dd4d0fc4a2685