feat: add tabs.onRemoved and tabs.onCreated mocks

[RickyMarou]

I took a (very) quick stab at adding those missing methods:

• tabs.onCreated
• tabs.onRemoved

I followed the existing pattern that exists with onUpdated, i.e. I did not implement mock functionalities to make the addListener, removeListener and hasListener work (we could for an example keep track of the functions added as listeners and return correct values in hasListener), but simply mocked them with jest.fn().