WIP: freedreno: move bind_sampler_states to per-generation

Keep the existing function as a common helper.  But this lets us move an
a2xx specific hack out of common code.  And the PIPE_TEX_WRAP_CLAMP
emulation will require an a3xx specific hack.  So rather than piling on
hacks, split this out.
WIP: freedreno: add texcoord clamp support to lowering

This is for hw that needs to emulate some texture wrap modes (like
CLAMP) with some help from the shader.
WIP: freedreno/a3xx: add support to emulate GL_CLAMP
WIP: freedreno/ir3: add some cmdline args
WIP: freedreno/a3xx: re-emit shaders on variant change

We need to keep track if a state change other than frag/vert shader
state will trigger us to need a different shader variant, and if
necessary mark the appropriate shader state as dirty.  Otherwise we will
forget to re-emit the shader state.