Parse fonts.xml when SystemFonts#getAvailableFonts is called

The fonts.xml is no longer parsed once we move to new model.
Thus, need to parse fonts.xml when SystemFonts#getAvailableFonts
is called.

Bug: 173752727
Test: atest NativeSystemFontTest
Change-Id: I628a2586f8450b942caf34ede5dc827e31fff0ef
1 file changed