ShortcutManager: deal with changing resource IDs on app update

- When an app is upgraded, all the resource IDs may change.  So
if a shortcut is previously published with an icon for res ID 100
and the publisher is upgraded, resource #100 may refer to something
different.

- So now the service also remembers resource names for icon resources,
as wells as string resources.  When an app is updated, the service
fetch the updated resource IDs by name.

- Also extract all string resources when a shortcut is published
and persist them, so that even when the original string resources are
removed from the app, the launcher can still show the extracted strings.

- When the system locale changes, re-extract all string resources.

- Also really hide the constants in ShortcutInfo that were
accidentally made public.

Change-Id: I23c29b45c1de5d76175229190a1533c9c62c5960