Structure MediaProvider as an APEX.

Based on guidance from the Mainline team, we're placing the
MediaProvider APK inside a new APEX, as this will allow us to
move MediaStore.java inside the module boundary in a future CL.

Bug: 144247087
Test: manual
Change-Id: I88f6f2e598d9611e8b92143504e4328d93671cab
diff --git a/apex/Android.bp b/apex/Android.bp
index 8eedfab..965bf31 100644
--- a/apex/Android.bp
+++ b/apex/Android.bp
@@ -77,6 +77,13 @@
 }
 
 filegroup {
+  name: "com.android.mediaprovider-file_contexts",
+  srcs: [
+    "com.android.mediaprovider-file_contexts",
+  ],
+}
+
+filegroup {
   name: "com.android.media.swcodec-file_contexts",
   srcs: [
     "com.android.media.swcodec-file_contexts",
diff --git a/apex/com.android.mediaprovider-file_contexts b/apex/com.android.mediaprovider-file_contexts
new file mode 100644
index 0000000..f6b21da
--- /dev/null
+++ b/apex/com.android.mediaprovider-file_contexts
@@ -0,0 +1,2 @@
+(/.*)?                u:object_r:system_file:s0
+/lib(64)?(/.*)        u:object_r:system_lib_file:s0