This came out of discussions about Boolean type weirdness in !20509 (merged). Basically, all of these helpers assume they're being run after nir_lower_bool_to_int32 on hardware that wants that. However, dozen does not want that, and it had just been working by luck.
While investigating that, I noticed that i915 has needs that aren't being met by these passes. It wants Boolean values as float32, and this mismatch causes it to crash on AA point tests. D'oh!
These changes allow drivers using these helpers to specify what kind of Boolean values it wants for AA points and polygon stipple. Those seem to be the only cases that generate Booleans.