Automatically grant URI permission as needed.

With this CL, the system automatically grants a temporary URI permission
to the target application when the IME calls
InputConnection#commitContent() with
InputConnection#INPUT_CONTENT_GRANT_READ_URI_PERMISSION.  The temporary
permission will be revoked by any of the following events:
 - InputContentInfo#releasePermission() is explicitly called by the
   target application.
 - The target application returned false in
   InputConnection#commitContent().
 - All the InputContentInfo instances copied from the original one are
   GC-ed.

If we do not do this and there is an application that forgot to call
that method then there is no way for IME developers to prevent
permission denial from happening in the application except for relaxing
the default permission of the ContentProvider just because of such an
application.

Although application developers are still expected to explicitly call
InputContentInfo#{request,release}Permission(), forgetting to call
InputContentInfo#requestPermission() does not hurt the user anymore.

With this CL, calling InputContentInfo#requestPermission() after calling
InputContentInfo#releasePermission() is also allowed.

Bug: 29892936
Change-Id: Id955435dd2e72549ee7134f46b3c6951581694ad