Add native font enumeration API implementation

ASystemFont API provides an ability of enumerating the system available
font files with some additional information.

ASystemFont reads /system/etc/fonts.xml and give the information to
developers.

Lots of developers reads fonts.xml by themselves but that is not a part
of public API and the structure is subject to change. This API is a
replacement of the reading fonts.xml by developers.

Bug: 111861508
Test: atest NativeSystemFontTest

Change-Id: I992902228650303eb10f486f1ec7838f218c15e7
diff --git a/native/android/Android.bp b/native/android/Android.bp
index 43847cc..24d003b 100644
--- a/native/android/Android.bp
+++ b/native/android/Android.bp
@@ -49,6 +49,7 @@
         "sharedmem.cpp",
         "storage_manager.cpp",
         "surface_texture.cpp",
+        "system_fonts.cpp",
         "trace.cpp",
     ],
 
@@ -65,6 +66,7 @@
         "libandroid_runtime",
         "libnetd_client",
         "libhwui",
+        "libxml2",
     ],
 
     static_libs: [