Adjustments after moving MediaStore inside APEX.

The "core_platform" SDK technically includes non-stable APIs, so we
need to shift to "core_current" instead.

While we're here, tidy up some older @removed APIs that never shipped
and replace HexEncoding with a local implementation.

Since MediaProvider itself is free to use @hide APIs from its own
framework code in MediaStore.java, we can include all sources
from "framework-mediaprovider-sources" directly.

Bug: 144247087
Test: atest --test-mapping packages/providers/MediaProvider
Change-Id: Iab806e7f685fc80411a78289bcc906c612e1fa6c
diff --git a/apex/framework/Android.bp b/apex/framework/Android.bp
index be2c55d..67c02ae 100644
--- a/apex/framework/Android.bp
+++ b/apex/framework/Android.bp
@@ -25,7 +25,7 @@
 
     installable: true,
 
-    sdk_version: "core_platform",
+    sdk_version: "core_current",
     libs: [
         // The order matters. android_system_* library should come later.
         "framework_mediaprovider_annotation",
@@ -63,4 +63,5 @@
     name: "framework_mediaprovider_annotation",
     srcs: [":framework-mediaprovider-annotation-sources"],
     installable: false,
+    sdk_version: "core_current",
 }