freedreno/ir3: split out shader compiler from a3xx

freedreno/ir3: split out shader compiler from a3xx

Move the bits we want to share between generations from fd3_program to
ir3_shader.  So overall structure is:

  fdN_shader_stateobj -> ir3_shader -> ir3_shader_variant -> ir3
                                    |- ...
                                    \- ir3_shader_variant -> ir3

So the ir3_shader becomes the topmost generation neutral object, which
manages the set of variants each of which generates, compiles, and
assembles it's own ir.

There is a bit of additional renaming to s/fd3_compiler/ir3_compiler/,
etc.

Keep the split between the gallium level stateobj and the shader helper
object because it might be a good idea to pre-compute some generation
specific register values (ie. anything that is independent of linking).

Signed-off-by: Rob Clark <robclark@freedesktop.org>