intel/fs,vec4: Stuff the constant data from NIR in the end of the program
This effectively gives our shaders a .data section in which to store the constant data. The motivation for this is the ANV patch at the end. Passing all that data around and caching it is really quite painful. It's way more convenient for us if it's just part of the binary.
I've not written the obvious iris patch. @kwg, would this help at all there?