vulkan/runtime: Add a level field to vk_command_buffer

Looks like 3 implementations already have that field in their private
command_buffer struct, and having it at the vk_command_buffer opens the
door for generic (but suboptimal) secondary command buffer support.

Reviewed-by: Jason Ekstrand <jason.ekstrand@collabora.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14917>

src/vulkan/runtime/vk_command_buffer.c

@@ -25,12 +25,14 @@
 
 VkResult
 vk_command_buffer_init(struct vk_command_buffer *command_buffer,
-                       struct vk_device *device)
+                       struct vk_device *device,
+                       VkCommandBufferLevel level)
 {
    memset(command_buffer, 0, sizeof(*command_buffer));
    vk_object_base_init(device, &command_buffer->base,
                        VK_OBJECT_TYPE_COMMAND_BUFFER);
 
+   command_buffer->level = level;
    util_dynarray_init(&command_buffer->labels, NULL);
    command_buffer->region_begin = true;