A couple of months ago I raided a village that also seemed to keep repopulating. While the current batch were distracted elsewhere, I snuck in, took a look around, and noticed that there were two Fuling Totems on altars. After destroying the altars and taking the Totems (it was the only change I made to the village), respawns stopped.

A month ago, I came across a Fuling tower on the edge of a meadows/plains border that also kept respawning Fulings. Tower had the same altar inside it and, again, respawns stopped after I destroyed it (again, only change before the respawns stopped).

Obviously this is merely two points of experience from a single player and therefore not particularly scientific. Take it as you please.

So, yes, there does seem to be a spawner, no, it does not appear to be a permanent thing.