nir: Factor out most of the algebraic passes C code to .c/.h.

nir: Factor out most of the algebraic passes C code to .c/.h.

Working on the algebraic implementation, I was being driven nuts by my
editor not highlighting and handling indentation for the C code.  It turns
out that it's basically not pass-specific code, and we can move it over to
the relevant .c file.  Replaces 30KB of code with 34KB of data on my i965
build.  No perf diff on shader-db (n=3)

Reviewed-by: Ian Romanick <ian.d.romainck@intel.com>
Reviewed-by: Connor Abbott <cwabbott0@gmail.com>