mesa/st: call _mesa_initialize() early

This allows drivers to reliably do things like using the GLSL
type-system during initialization.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4765>

src/mesa/state_tracker/st_manager.c

@@ -894,6 +894,8 @@ st_api_create_context(struct st_api *stapi, struct st_manager *smapi,
       return NULL;
    }
 
+   _mesa_initialize();
+
    /* Create a hash table for the framebuffer interface objects
     * if it has not been created for this st manager.
     */