i965: Rework gl_TessLevel*[] handling to use NIR compact arrays.

i965: Rework gl_TessLevel*[] handling to use NIR compact arrays.

Treating everything as scalar arrays allows us to drop a bunch of
special case input/output munging all throughout the backend.
Instead, we just need to remap the TessLevel components to the
appropriate patch URB header locations in remap_patch_urb_offsets().

We also switch to treating the TES input versions of these as ordinary
shader inputs rather than system values, as remap_patch_urb_offsets()
just makes everything work out without special handling.

This regresses one Piglit test:
arb_tessellation_shader-large-uniforms/GL_TESS_CONTROL_SHADER-array-at-limit

The compiler starts promoting the constant arrays assigned to gl_TessLevel*
to uniform arrays.  Since the shader also has a uniform array that uses
the maximum number of uniform components, this puts it over the uniform
component limit enforced by the linker.  This is arguably a bug in the
constant array promotion code (it should avoid pushing us over limits),
but is unlikely to penalize any real application.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>