Move MediaStore.java inside APEX boundary.

Recent work has paved the way to get MediaStore.java building against
"core_platform", and this change is actually shifting MediaStore.java
inside the MediaProvider APEX boundary.

This involves defining a new "updatable-mediaprovider" library JAR
and ensuring that it's spliced into classpaths where needed to keep
everything building and working.

Note that the MediaProvider APK itself is still bundled, so we're
manually including the MediaStore.java when building that APK so that
we can continue referencing @hide symbols, but there's a STOPSHIP
comment to remove that once we get the APK building against
"system_current".

Bug: 144247087
Test: atest --test-mapping packages/providers/MediaProvider
Change-Id: I6d6da165848b934f4ca7ecfca7b97de6f97897e3
diff --git a/java/config/config.go b/java/config/config.go
index 8443693..88d9411 100644
--- a/java/config/config.go
+++ b/java/config/config.go
@@ -47,6 +47,7 @@
 		"core-oj",
 		"core-libart",
 		"updatable-media",
+		"framework-mediaprovider",
 		"ike",
 	}
 )