Oh. You were expecting a clear-cut definition of something from law? Residency is a loose term in Washington State. The law basically says, "You know what we mean," and then expects you to know what they mean. If, for example, you were to be charged for carrying a concealed pistol, it would be up to you to prove that you had
not established residency, and were therefore legally licensed with your Virginia or Utah licenses.
The reason I used the delightfully-snarky LMGTFY is because this explanation is readily available from a simple Google search if you actually use the search results instead of selectively filtering them looking for some clear-cut definition in state law which does not exist (nor does it in many states). The state presumes a reasonable person will
know pornography when they see it, and they leave it to you to make sure you err on the safe side.
Simple version: if you want to carry concealed on your Virginia or Utah licenses, don't rent or buy an apartment or house, don't pay a utility bill on a Washington address, and don't get a Washington driver's license. If you want to get more nuanced than that, go spend money on a lawyer.