Make sure that all types are accessible

[agi]

Just noticed: apilint should make sure that all types in the API are accessible (e.g. using a private type in a method argument should not be allowed).

[agi]

Example here: https://searchfox.org/mozilla-central/rev/2cc3b39bc9bb024d35e09e9c8acecf0e2dfb4e13/mobile/android/geckoview/api.txt#1818 the Builder class is package protected so that method should not be allowed