Added better asserts to IPA, Renamed IPA modes to match mesa

IpaMode is changed to IpaInterpMode
IpaMode is suppose to be 2 bits not 3
Added IpaSampleMode
Added Saturate

Renamed modes based on
https://github.com/mesa3d/mesa/blob/d27c7918916cdc8092959124955f887592e37d72/src/gallium/drivers/nouveau/codegen/nv50_ir_emit_gm107.cpp#L2530