Remove the public APIs for allow rich content.

1. Marked @hide for "Drawable loadAnimatedImage(Context)" and "String loadHtmlDescription(PackageManager)".
2. Move common function into util.

Bug: 149516547
Bug: 142532186
Test: maunal test & atest AccessibilityServiceInfoTest -c
Change-Id: I06e8d69b6f78eb1af4f024e239e0837b95285bbc
Merged-In: I06e8d69b6f78eb1af4f024e239e0837b95285bbc
(cherry picked from commit 4c367c7abf65bf844bce8ecb65275636e35887f8)
1 file changed