Add checking values not to save illegal value to appwidgets.xml

Symptom:
All AppWidgets on Home screen disppear after appwidgets.xml updated
with invalid value.

Root cause:
The issue occurs when size information of an AppWidget is set to 0
via AppWidgetHostView#updateAppWidgetSize() API.
Since width and height are taken positive padding, so they become
negative number and are sent to
AppWidgetServiceImpl#updateAppWidgetOptions().
In updateAppWidgetOptions(), convert values by
Integer.toHexString() to save widget parameters to appwidgets.xml,
but negative numbers become illegal values for Integer.parseInt().
After device is rebooted, widgets cannot be reloaded because parsing
appwidgets.xml fail by NumberFormatException at Integer.parseInt().

Solution:
When writing the widget's info to appwidgets.xml, check the size
parameters and replace with 0 if they're negative value.

Bug: 65705916

Change-Id: I48f69fbf081201a176ea1093094ba6cdb120e5f5