Introduces an `idx_count` field to `struct vkd3d_shader_register`. Another patch set is needed for further validations and to use this field where applicable.
-- v7: vkd3d-shader/tpf: Validate input and output index ranges for default control point phases. vkd3d-shader/tpf: Remove an unnecessary carriage return from a parser error message. vkd3d-shader/tpf: Validate index range declarations.