d3d11: Implement d3d11_input_layout_to_wined3d_declaration() on top of vkd3d_shader_parse_input_signature().
This was originally prompted by the fact that wined3d_extract_shader_input_signature_from_dxbc() allocates elements with HeapAlloc(), but d3d11_input_layout_to_wined3d_declaration() attempts to free them with free(). That's a regression introduced by commit b951c37b8791ceb052c9e159ad7927f75a72d667. Since we're touching the code though, we may as well use vkd3d_shader_parse_input_signature(), and get rid of wined3d_extract_shader_input_signature_from_dxbc().