kopper: Use the swap interval that was set at swapchain creation time.

We need to track what the caller has given us for swap interval, and use
that to set the present mode at startup.

Fixes incorrect vblank syncing in apitrace's glretrace, which sets the
swap interval to 0 before the swapchain is made.

Reviewed-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17470>

include/kopper_interface.h

@@ -95,6 +95,7 @@ struct kopper_loader_info {
 #endif
    };
    int has_alpha;
+   int initial_swap_interval;
 };
 
 #define __DRI_KOPPER_LOADER "DRI_KopperLoader"