Cleanup widgetsModel and add tests

1. Removes unused method `getAllWidgetComponentsWithoutShortcuts`
2. Exposes widgets either as component map or package item map - to
eliminate the duplicate logic around widget sections.
3. Add tests that validate that each package is unique - to help
cover the redirect issue seen in past.
4. In follow up cls, other methods that deal with picker specific data
types like WidgetsListBaseEntry will also be moved out - leaving the
model to only be responsible for providing all widgets map or widgets
by package.

Bug: 341611976
Flag: EXEMPT BUGFIX
Test: Unit test
Change-Id: Ife70874d312b51c66025a6ec678480f2b5c41793