Add Package Type field and filter on Packages page

[mjherzog]

When working with a large number of Packages it would be very helpful to add a Package Type field and enable filtering on it.

• When I search for pkg:type, e.g., "pkg-alpine or "pkg-npm", I get "No Packages found".
• When I search for just "alpine" or "npm" I do get a list.

[tdruez]

The advanced search is available for filtering on any of the model fields.
Ideally, we would have more UI around it to help define the filter values, but in the short term you can use the search box, eg: type:npm