d3d12: support rendering primitives with adjacency
I'm not sure how we didn't get busted wide open by the CTS for not supporting this, but seems we didn't. Anyway, let's support primitives with adjacency.
Fixes the following piglits:
- spec@glsl-1.50@arb_geometry_shader4-ignore-adjacent-vertices core gl_line_strip_adjacency
- spec@glsl-1.50@arb_geometry_shader4-ignore-adjacent-vertices core gl_lines_adjacency
- spec@glsl-1.50@arb_geometry_shader4-ignore-adjacent-vertices core gl_triangle_strip_adjacency
- spec@glsl-1.50@arb_geometry_shader4-ignore-adjacent-vertices core gl_triangles_adjacency
- spec@glsl-1.50@arb_geometry_shader4-ignore-adjacent-vertices core indexed gl_line_strip_adjacency
- spec@glsl-1.50@arb_geometry_shader4-ignore-adjacent-vertices core indexed gl_lines_adjacency
- spec@glsl-1.50@arb_geometry_shader4-ignore-adjacent-vertices core indexed gl_triangle_strip_adjacency
- spec@glsl-1.50@arb_geometry_shader4-ignore-adjacent-vertices core indexed gl_triangles_adjacency
- spec@glsl-1.50@execution@geometry@primitive-id-restart gl_line_strip_adjacency ffs
- spec@glsl-1.50@execution@geometry@primitive-id-restart gl_line_strip_adjacency other
- spec@glsl-1.50@execution@geometry@primitive-id-restart gl_lines_adjacency ffs
- spec@glsl-1.50@execution@geometry@primitive-id-restart gl_lines_adjacency other
- spec@glsl-1.50@execution@geometry@primitive-id-restart gl_triangle_strip_adjacency ffs
- spec@glsl-1.50@execution@geometry@primitive-id-restart gl_triangle_strip_adjacency other
- spec@glsl-1.50@execution@geometry@primitive-id-restart gl_triangles_adjacency ffs
- spec@glsl-1.50@execution@geometry@primitive-id-restart gl_triangles_adjacency other
- spec@glsl-1.50@execution@geometry@primitive-types gl_line_strip_adjacency
- spec@glsl-1.50@execution@geometry@primitive-types gl_lines_adjacency
- spec@glsl-1.50@execution@geometry@primitive-types gl_triangles_adjacency