Tweak LauncherApps API based on feedback

UserHandle must be after packageName/componentName.
Improved javadoc for density.
Added getApplicationInfo().
Remove synchronized methods.

Temporarily @hide the old APIs to make sure they continue to work
for unbundled launchers.

Bug: 15025908
Change-Id: Iee6336b54e1b4d5c43f1e643062327ff463cb695