Fix interpolation issues on HW

[eliasdaler]

Had an issue that only showed up on HW and now in emulators. Turns out it was caused by unsafe write before dpct.
https://github.com/user-attachments/assets/aec0b48b-a2d5-4cce-ae55-ec48a3939f64
(the flickering vertex colors when doing interpolation)

Also added some safeguards against bad psyqo::Color being passed into the primitives when it can potentially affect the command (e.g. in setColor/setColorA).
E.g. consider this case:

psyqo::Color c;
c.r = 0xAB;
c.g = 0xCD;
c.b = 0xEF;
// the value of c.packed is <??>EFCDAB

Or you could possibly read the color from some RGB register and if it has the MSB set... you'd get tons of corruptions and crashes on HW. To prevent that, we need to mask away those potentially "dirty" bits in everything.