gallium: add flag to draw info to indicate converted draws

this draw mode in particular requires driver-specific conversions
for queries (e.g., number of vertices), so pass that info through

the only limitation is that it doesn't work for dlists,
but I have yet to see a real use case of a statistics query being used with dlists

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15326>

src/gallium/include/pipe/p_state.h

@@ -845,7 +845,8 @@ struct pipe_draw_info
    bool take_index_buffer_ownership:1; /**< callee inherits caller's refcount
          (no need to reference indexbuf, but still needs to unreference it) */
    bool index_bias_varies:1;   /**< true if index_bias varies between draws */
-   uint8_t _pad:2;
+   bool was_line_loop:1; /**< true if pipe_prim_type was LINE_LOOP before translation */
+   uint8_t _pad:1;
 
    unsigned start_instance; /**< first instance id */
    unsigned instance_count; /**< number of instances */